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-rw-r--r--system/xen/xen.SlackBuild2
-rw-r--r--system/xen/xsa/xsa401-4.16-1.patch170
-rw-r--r--system/xen/xsa/xsa401-4.16-2.patch191
-rw-r--r--system/xen/xsa/xsa402-4.16-1.patch43
-rw-r--r--system/xen/xsa/xsa402-4.16-2.patch213
-rw-r--r--system/xen/xsa/xsa402-4.16-3.patch284
-rw-r--r--system/xen/xsa/xsa402-4.16-4.patch83
-rw-r--r--system/xen/xsa/xsa402-4.16-5.patch148
8 files changed, 1133 insertions, 1 deletions
diff --git a/system/xen/xen.SlackBuild b/system/xen/xen.SlackBuild
index 1d1d31d344dd..e504dc97bf12 100644
--- a/system/xen/xen.SlackBuild
+++ b/system/xen/xen.SlackBuild
@@ -26,7 +26,7 @@ cd $(dirname $0) ; CWD=$(pwd)
PRGNAM=xen
VERSION=${VERSION:-4.16.1}
-BUILD=${BUILD:-1}
+BUILD=${BUILD:-2}
TAG=${TAG:-_SBo}
PKGTYPE=${PKGTYPE:-tgz}
diff --git a/system/xen/xsa/xsa401-4.16-1.patch b/system/xen/xsa/xsa401-4.16-1.patch
new file mode 100644
index 000000000000..5c8c50617a21
--- /dev/null
+++ b/system/xen/xsa/xsa401-4.16-1.patch
@@ -0,0 +1,170 @@
+From: Andrew Cooper <andrew.cooper3@citrix.com>
+Subject: x86/pv: Clean up _get_page_type()
+
+Various fixes for clarity, ahead of making complicated changes.
+
+ * Split the overflow check out of the if/else chain for type handling, as
+ it's somewhat unrelated.
+ * Comment the main if/else chain to explain what is going on. Adjust one
+ ASSERT() and state the bit layout for validate-locked and partial states.
+ * Correct the comment about TLB flushing, as it's backwards. The problem
+ case is when writeable mappings are retained to a page becoming read-only,
+ as it allows the guest to bypass Xen's safety checks for updates.
+ * Reduce the scope of 'y'. It is an artefact of the cmpxchg loop and not
+ valid for use by subsequent logic. Switch to using ACCESS_ONCE() to treat
+ all reads as explicitly volatile. The only thing preventing the validated
+ wait-loop being infinite is the compiler barrier hidden in cpu_relax().
+ * Replace one page_get_owner(page) with the already-calculated 'd' already in
+ scope.
+
+No functional change.
+
+This is part of XSA-401 / CVE-2022-26362.
+
+Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
+Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
+Reviewed-by: Jan Beulich <jbeulich@suse.com>
+Reviewed-by: George Dunlap <george.dunlap@citrix.com>
+
+diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
+index 796faca64103..ddd32f88c798 100644
+--- a/xen/arch/x86/mm.c
++++ b/xen/arch/x86/mm.c
+@@ -2935,16 +2935,17 @@ static int _put_page_type(struct page_info *page, unsigned int flags,
+ static int _get_page_type(struct page_info *page, unsigned long type,
+ bool preemptible)
+ {
+- unsigned long nx, x, y = page->u.inuse.type_info;
++ unsigned long nx, x;
+ int rc = 0;
+
+ ASSERT(!(type & ~(PGT_type_mask | PGT_pae_xen_l2)));
+ ASSERT(!in_irq());
+
+- for ( ; ; )
++ for ( unsigned long y = ACCESS_ONCE(page->u.inuse.type_info); ; )
+ {
+ x = y;
+ nx = x + 1;
++
+ if ( unlikely((nx & PGT_count_mask) == 0) )
+ {
+ gdprintk(XENLOG_WARNING,
+@@ -2952,8 +2953,15 @@ static int _get_page_type(struct page_info *page, unsigned long type,
+ mfn_x(page_to_mfn(page)));
+ return -EINVAL;
+ }
+- else if ( unlikely((x & PGT_count_mask) == 0) )
++
++ if ( unlikely((x & PGT_count_mask) == 0) )
+ {
++ /*
++ * Typeref 0 -> 1.
++ *
++ * Type changes are permitted when the typeref is 0. If the type
++ * actually changes, the page needs re-validating.
++ */
+ struct domain *d = page_get_owner(page);
+
+ if ( d && shadow_mode_enabled(d) )
+@@ -2964,8 +2972,8 @@ static int _get_page_type(struct page_info *page, unsigned long type,
+ {
+ /*
+ * On type change we check to flush stale TLB entries. It is
+- * vital that no other CPUs are left with mappings of a frame
+- * which is about to become writeable to the guest.
++ * vital that no other CPUs are left with writeable mappings
++ * to a frame which is intending to become pgtable/segdesc.
+ */
+ cpumask_t *mask = this_cpu(scratch_cpumask);
+
+@@ -2977,7 +2985,7 @@ static int _get_page_type(struct page_info *page, unsigned long type,
+
+ if ( unlikely(!cpumask_empty(mask)) &&
+ /* Shadow mode: track only writable pages. */
+- (!shadow_mode_enabled(page_get_owner(page)) ||
++ (!shadow_mode_enabled(d) ||
+ ((nx & PGT_type_mask) == PGT_writable_page)) )
+ {
+ perfc_incr(need_flush_tlb_flush);
+@@ -3008,7 +3016,14 @@ static int _get_page_type(struct page_info *page, unsigned long type,
+ }
+ else if ( unlikely((x & (PGT_type_mask|PGT_pae_xen_l2)) != type) )
+ {
+- /* Don't log failure if it could be a recursive-mapping attempt. */
++ /*
++ * else, we're trying to take a new reference, of the wrong type.
++ *
++ * This (being able to prohibit use of the wrong type) is what the
++ * typeref system exists for, but skip printing the failure if it
++ * looks like a recursive mapping, as subsequent logic might
++ * ultimately permit the attempt.
++ */
+ if ( ((x & PGT_type_mask) == PGT_l2_page_table) &&
+ (type == PGT_l1_page_table) )
+ return -EINVAL;
+@@ -3027,18 +3042,46 @@ static int _get_page_type(struct page_info *page, unsigned long type,
+ }
+ else if ( unlikely(!(x & PGT_validated)) )
+ {
++ /*
++ * else, the count is non-zero, and we're grabbing the right type;
++ * but the page hasn't been validated yet.
++ *
++ * The page is in one of two states (depending on PGT_partial),
++ * and should have exactly one reference.
++ */
++ ASSERT((x & (PGT_type_mask | PGT_count_mask)) == (type | 1));
++
+ if ( !(x & PGT_partial) )
+ {
+- /* Someone else is updating validation of this page. Wait... */
++ /*
++ * The page has been left in the "validate locked" state
++ * (i.e. PGT_[type] | 1) which means that a concurrent caller
++ * of _get_page_type() is in the middle of validation.
++ *
++ * Spin waiting for the concurrent user to complete (partial
++ * or fully validated), then restart our attempt to acquire a
++ * type reference.
++ */
+ do {
+ if ( preemptible && hypercall_preempt_check() )
+ return -EINTR;
+ cpu_relax();
+- } while ( (y = page->u.inuse.type_info) == x );
++ } while ( (y = ACCESS_ONCE(page->u.inuse.type_info)) == x );
+ continue;
+ }
+- /* Type ref count was left at 1 when PGT_partial got set. */
+- ASSERT((x & PGT_count_mask) == 1);
++
++ /*
++ * The page has been left in the "partial" state
++ * (i.e., PGT_[type] | PGT_partial | 1).
++ *
++ * Rather than bumping the type count, we need to try to grab the
++ * validation lock; if we succeed, we need to validate the page,
++ * then drop the general ref associated with the PGT_partial bit.
++ *
++ * We grab the validation lock by setting nx to (PGT_[type] | 1)
++ * (i.e., non-zero type count, neither PGT_validated nor
++ * PGT_partial set).
++ */
+ nx = x & ~PGT_partial;
+ }
+
+@@ -3087,6 +3130,13 @@ static int _get_page_type(struct page_info *page, unsigned long type,
+ }
+
+ out:
++ /*
++ * Did we drop the PGT_partial bit when acquiring the typeref? If so,
++ * drop the general reference that went along with it.
++ *
++ * N.B. validate_page() may have have re-set PGT_partial, not reflected in
++ * nx, but will have taken an extra ref when doing so.
++ */
+ if ( (x & PGT_partial) && !(nx & PGT_partial) )
+ put_page(page);
+
diff --git a/system/xen/xsa/xsa401-4.16-2.patch b/system/xen/xsa/xsa401-4.16-2.patch
new file mode 100644
index 000000000000..be58db59a513
--- /dev/null
+++ b/system/xen/xsa/xsa401-4.16-2.patch
@@ -0,0 +1,191 @@
+From: Andrew Cooper <andrew.cooper3@citrix.com>
+Subject: x86/pv: Fix ABAC cmpxchg() race in _get_page_type()
+
+_get_page_type() suffers from a race condition where it incorrectly assumes
+that because 'x' was read and a subsequent a cmpxchg() succeeds, the type
+cannot have changed in-between. Consider:
+
+CPU A:
+ 1. Creates an L2e referencing pg
+ `-> _get_page_type(pg, PGT_l1_page_table), sees count 0, type PGT_writable_page
+ 2. Issues flush_tlb_mask()
+CPU B:
+ 3. Creates a writeable mapping of pg
+ `-> _get_page_type(pg, PGT_writable_page), count increases to 1
+ 4. Writes into new mapping, creating a TLB entry for pg
+ 5. Removes the writeable mapping of pg
+ `-> _put_page_type(pg), count goes back down to 0
+CPU A:
+ 7. Issues cmpxchg(), setting count 1, type PGT_l1_page_table
+
+CPU B now has a writeable mapping to pg, which Xen believes is a pagetable and
+suitably protected (i.e. read-only). The TLB flush in step 2 must be deferred
+until after the guest is prohibited from creating new writeable mappings,
+which is after step 7.
+
+Defer all safety actions until after the cmpxchg() has successfully taken the
+intended typeref, because that is what prevents concurrent users from using
+the old type.
+
+Also remove the early validation for writeable and shared pages. This removes
+race conditions where one half of a parallel mapping attempt can return
+successfully before:
+ * The IOMMU pagetables are in sync with the new page type
+ * Writeable mappings to shared pages have been torn down
+
+This is part of XSA-401 / CVE-2022-26362.
+
+Reported-by: Jann Horn <jannh@google.com>
+Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
+Reviewed-by: Jan Beulich <jbeulich@suse.com>
+Reviewed-by: George Dunlap <george.dunlap@citrix.com>
+
+diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
+index ddd32f88c798..1693b580b152 100644
+--- a/xen/arch/x86/mm.c
++++ b/xen/arch/x86/mm.c
+@@ -2962,56 +2962,12 @@ static int _get_page_type(struct page_info *page, unsigned long type,
+ * Type changes are permitted when the typeref is 0. If the type
+ * actually changes, the page needs re-validating.
+ */
+- struct domain *d = page_get_owner(page);
+-
+- if ( d && shadow_mode_enabled(d) )
+- shadow_prepare_page_type_change(d, page, type);
+
+ ASSERT(!(x & PGT_pae_xen_l2));
+ if ( (x & PGT_type_mask) != type )
+ {
+- /*
+- * On type change we check to flush stale TLB entries. It is
+- * vital that no other CPUs are left with writeable mappings
+- * to a frame which is intending to become pgtable/segdesc.
+- */
+- cpumask_t *mask = this_cpu(scratch_cpumask);
+-
+- BUG_ON(in_irq());
+- cpumask_copy(mask, d->dirty_cpumask);
+-
+- /* Don't flush if the timestamp is old enough */
+- tlbflush_filter(mask, page->tlbflush_timestamp);
+-
+- if ( unlikely(!cpumask_empty(mask)) &&
+- /* Shadow mode: track only writable pages. */
+- (!shadow_mode_enabled(d) ||
+- ((nx & PGT_type_mask) == PGT_writable_page)) )
+- {
+- perfc_incr(need_flush_tlb_flush);
+- /*
+- * If page was a page table make sure the flush is
+- * performed using an IPI in order to avoid changing the
+- * type of a page table page under the feet of
+- * spurious_page_fault().
+- */
+- flush_mask(mask,
+- (x & PGT_type_mask) &&
+- (x & PGT_type_mask) <= PGT_root_page_table
+- ? FLUSH_TLB | FLUSH_FORCE_IPI
+- : FLUSH_TLB);
+- }
+-
+- /* We lose existing type and validity. */
+ nx &= ~(PGT_type_mask | PGT_validated);
+ nx |= type;
+-
+- /*
+- * No special validation needed for writable pages.
+- * Page tables and GDT/LDT need to be scanned for validity.
+- */
+- if ( type == PGT_writable_page || type == PGT_shared_page )
+- nx |= PGT_validated;
+ }
+ }
+ else if ( unlikely((x & (PGT_type_mask|PGT_pae_xen_l2)) != type) )
+@@ -3092,6 +3048,56 @@ static int _get_page_type(struct page_info *page, unsigned long type,
+ return -EINTR;
+ }
+
++ /*
++ * One typeref has been taken and is now globally visible.
++ *
++ * The page is either in the "validate locked" state (PGT_[type] | 1) or
++ * fully validated (PGT_[type] | PGT_validated | >0).
++ */
++
++ if ( unlikely((x & PGT_count_mask) == 0) )
++ {
++ struct domain *d = page_get_owner(page);
++
++ if ( d && shadow_mode_enabled(d) )
++ shadow_prepare_page_type_change(d, page, type);
++
++ if ( (x & PGT_type_mask) != type )
++ {
++ /*
++ * On type change we check to flush stale TLB entries. It is
++ * vital that no other CPUs are left with writeable mappings
++ * to a frame which is intending to become pgtable/segdesc.
++ */
++ cpumask_t *mask = this_cpu(scratch_cpumask);
++
++ BUG_ON(in_irq());
++ cpumask_copy(mask, d->dirty_cpumask);
++
++ /* Don't flush if the timestamp is old enough */
++ tlbflush_filter(mask, page->tlbflush_timestamp);
++
++ if ( unlikely(!cpumask_empty(mask)) &&
++ /* Shadow mode: track only writable pages. */
++ (!shadow_mode_enabled(d) ||
++ ((nx & PGT_type_mask) == PGT_writable_page)) )
++ {
++ perfc_incr(need_flush_tlb_flush);
++ /*
++ * If page was a page table make sure the flush is
++ * performed using an IPI in order to avoid changing the
++ * type of a page table page under the feet of
++ * spurious_page_fault().
++ */
++ flush_mask(mask,
++ (x & PGT_type_mask) &&
++ (x & PGT_type_mask) <= PGT_root_page_table
++ ? FLUSH_TLB | FLUSH_FORCE_IPI
++ : FLUSH_TLB);
++ }
++ }
++ }
++
+ if ( unlikely(((x & PGT_type_mask) == PGT_writable_page) !=
+ (type == PGT_writable_page)) )
+ {
+@@ -3120,13 +3126,25 @@ static int _get_page_type(struct page_info *page, unsigned long type,
+
+ if ( unlikely(!(nx & PGT_validated)) )
+ {
+- if ( !(x & PGT_partial) )
++ /*
++ * No special validation needed for writable or shared pages. Page
++ * tables and GDT/LDT need to have their contents audited.
++ *
++ * per validate_page(), non-atomic updates are fine here.
++ */
++ if ( type == PGT_writable_page || type == PGT_shared_page )
++ page->u.inuse.type_info |= PGT_validated;
++ else
+ {
+- page->nr_validated_ptes = 0;
+- page->partial_flags = 0;
+- page->linear_pt_count = 0;
++ if ( !(x & PGT_partial) )
++ {
++ page->nr_validated_ptes = 0;
++ page->partial_flags = 0;
++ page->linear_pt_count = 0;
++ }
++
++ rc = validate_page(page, type, preemptible);
+ }
+- rc = validate_page(page, type, preemptible);
+ }
+
+ out:
diff --git a/system/xen/xsa/xsa402-4.16-1.patch b/system/xen/xsa/xsa402-4.16-1.patch
new file mode 100644
index 000000000000..b783383fc89f
--- /dev/null
+++ b/system/xen/xsa/xsa402-4.16-1.patch
@@ -0,0 +1,43 @@
+From: Andrew Cooper <andrew.cooper3@citrix.com>
+Subject: x86/page: Introduce _PAGE_* constants for memory types
+
+... rather than opencoding the PAT/PCD/PWT attributes in __PAGE_HYPERVISOR_*
+constants. These are going to be needed by forthcoming logic.
+
+No functional change.
+
+This is part of XSA-402.
+
+Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
+Reviewed-by: Jan Beulich <jbeulich@suse.com>
+
+diff --git a/xen/include/asm-x86/page.h b/xen/include/asm-x86/page.h
+index 1d080cffbe84..2e542050f65a 100644
+--- a/xen/include/asm-x86/page.h
++++ b/xen/include/asm-x86/page.h
+@@ -331,6 +331,14 @@ void efi_update_l4_pgtable(unsigned int l4idx, l4_pgentry_t);
+
+ #define PAGE_CACHE_ATTRS (_PAGE_PAT | _PAGE_PCD | _PAGE_PWT)
+
++/* Memory types, encoded under Xen's choice of MSR_PAT. */
++#define _PAGE_WB ( 0)
++#define _PAGE_WT ( _PAGE_PWT)
++#define _PAGE_UCM ( _PAGE_PCD )
++#define _PAGE_UC ( _PAGE_PCD | _PAGE_PWT)
++#define _PAGE_WC (_PAGE_PAT )
++#define _PAGE_WP (_PAGE_PAT | _PAGE_PWT)
++
+ /*
+ * Debug option: Ensure that granted mappings are not implicitly unmapped.
+ * WARNING: This will need to be disabled to run OSes that use the spare PTE
+@@ -349,8 +357,8 @@ void efi_update_l4_pgtable(unsigned int l4idx, l4_pgentry_t);
+ #define __PAGE_HYPERVISOR_RX (_PAGE_PRESENT | _PAGE_ACCESSED)
+ #define __PAGE_HYPERVISOR (__PAGE_HYPERVISOR_RX | \
+ _PAGE_DIRTY | _PAGE_RW)
+-#define __PAGE_HYPERVISOR_UCMINUS (__PAGE_HYPERVISOR | _PAGE_PCD)
+-#define __PAGE_HYPERVISOR_UC (__PAGE_HYPERVISOR | _PAGE_PCD | _PAGE_PWT)
++#define __PAGE_HYPERVISOR_UCMINUS (__PAGE_HYPERVISOR | _PAGE_UCM)
++#define __PAGE_HYPERVISOR_UC (__PAGE_HYPERVISOR | _PAGE_UC)
+ #define __PAGE_HYPERVISOR_SHSTK (__PAGE_HYPERVISOR_RO | _PAGE_DIRTY)
+
+ #define MAP_SMALL_PAGES _PAGE_AVAIL0 /* don't use superpages mappings */
diff --git a/system/xen/xsa/xsa402-4.16-2.patch b/system/xen/xsa/xsa402-4.16-2.patch
new file mode 100644
index 000000000000..ebb2f5e221e8
--- /dev/null
+++ b/system/xen/xsa/xsa402-4.16-2.patch
@@ -0,0 +1,213 @@
+From: Andrew Cooper <andrew.cooper3@citrix.com>
+Subject: x86: Don't change the cacheability of the directmap
+
+Changeset 55f97f49b7ce ("x86: Change cache attributes of Xen 1:1 page mappings
+in response to guest mapping requests") attempted to keep the cacheability
+consistent between different mappings of the same page.
+
+The reason wasn't described in the changelog, but it is understood to be in
+regards to a concern over machine check exceptions, owing to errata when using
+mixed cacheabilities. It did this primarily by updating Xen's mapping of the
+page in the direct map when the guest mapped a page with reduced cacheability.
+
+Unfortunately, the logic didn't actually prevent mixed cacheability from
+occurring:
+ * A guest could map a page normally, and then map the same page with
+ different cacheability; nothing prevented this.
+ * The cacheability of the directmap was always latest-takes-precedence in
+ terms of guest requests.
+ * Grant-mapped frames with lesser cacheability didn't adjust the page's
+ cacheattr settings.
+ * The map_domain_page() function still unconditionally created WB mappings,
+ irrespective of the page's cacheattr settings.
+
+Additionally, update_xen_mappings() had a bug where the alias calculation was
+wrong for mfn's which were .init content, which should have been treated as
+fully guest pages, not Xen pages.
+
+Worse yet, the logic introduced a vulnerability whereby necessary
+pagetable/segdesc adjustments made by Xen in the validation logic could become
+non-coherent between the cache and main memory. The CPU could subsequently
+operate on the stale value in the cache, rather than the safe value in main
+memory.
+
+The directmap contains primarily mappings of RAM. PAT/MTRR conflict
+resolution is asymmetric, and generally for MTRR=WB ranges, PAT of lesser
+cacheability resolves to being coherent. The special case is WC mappings,
+which are non-coherent against MTRR=WB regions (except for fully-coherent
+CPUs).
+
+Xen must not have any WC cacheability in the directmap, to prevent Xen's
+actions from creating non-coherency. (Guest actions creating non-coherency is
+dealt with in subsequent patches.) As all memory types for MTRR=WB ranges
+inter-operate coherently, so leave Xen's directmap mappings as WB.
+
+Only PV guests with access to devices can use reduced-cacheability mappings to
+begin with, and they're trusted not to mount DoSs against the system anyway.
+
+Drop PGC_cacheattr_{base,mask} entirely, and the logic to manipulate them.
+Shift the later PGC_* constants up, to gain 3 extra bits in the main reference
+count. Retain the check in get_page_from_l1e() for special_pages() because a
+guest has no business using reduced cacheability on these.
+
+This reverts changeset 55f97f49b7ce6c3520c555d19caac6cf3f9a5df0
+
+This is CVE-2022-26363, part of XSA-402.
+
+Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
+Reviewed-by: George Dunlap <george.dunlap@citrix.com>
+
+diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
+index c6429b0f749a..ab32d13a1a0d 100644
+--- a/xen/arch/x86/mm.c
++++ b/xen/arch/x86/mm.c
+@@ -783,28 +783,6 @@ bool is_iomem_page(mfn_t mfn)
+ return (page_get_owner(page) == dom_io);
+ }
+
+-static int update_xen_mappings(unsigned long mfn, unsigned int cacheattr)
+-{
+- int err = 0;
+- bool alias = mfn >= PFN_DOWN(xen_phys_start) &&
+- mfn < PFN_UP(xen_phys_start + xen_virt_end - XEN_VIRT_START);
+- unsigned long xen_va =
+- XEN_VIRT_START + ((mfn - PFN_DOWN(xen_phys_start)) << PAGE_SHIFT);
+-
+- if ( boot_cpu_has(X86_FEATURE_XEN_SELFSNOOP) )
+- return 0;
+-
+- if ( unlikely(alias) && cacheattr )
+- err = map_pages_to_xen(xen_va, _mfn(mfn), 1, 0);
+- if ( !err )
+- err = map_pages_to_xen((unsigned long)mfn_to_virt(mfn), _mfn(mfn), 1,
+- PAGE_HYPERVISOR | cacheattr_to_pte_flags(cacheattr));
+- if ( unlikely(alias) && !cacheattr && !err )
+- err = map_pages_to_xen(xen_va, _mfn(mfn), 1, PAGE_HYPERVISOR);
+-
+- return err;
+-}
+-
+ #ifndef NDEBUG
+ struct mmio_emul_range_ctxt {
+ const struct domain *d;
+@@ -1009,47 +987,14 @@ get_page_from_l1e(
+ goto could_not_pin;
+ }
+
+- if ( pte_flags_to_cacheattr(l1f) !=
+- ((page->count_info & PGC_cacheattr_mask) >> PGC_cacheattr_base) )
++ if ( (l1f & PAGE_CACHE_ATTRS) != _PAGE_WB && is_special_page(page) )
+ {
+- unsigned long x, nx, y = page->count_info;
+- unsigned long cacheattr = pte_flags_to_cacheattr(l1f);
+- int err;
+-
+- if ( is_special_page(page) )
+- {
+- if ( write )
+- put_page_type(page);
+- put_page(page);
+- gdprintk(XENLOG_WARNING,
+- "Attempt to change cache attributes of Xen heap page\n");
+- return -EACCES;
+- }
+-
+- do {
+- x = y;
+- nx = (x & ~PGC_cacheattr_mask) | (cacheattr << PGC_cacheattr_base);
+- } while ( (y = cmpxchg(&page->count_info, x, nx)) != x );
+-
+- err = update_xen_mappings(mfn, cacheattr);
+- if ( unlikely(err) )
+- {
+- cacheattr = y & PGC_cacheattr_mask;
+- do {
+- x = y;
+- nx = (x & ~PGC_cacheattr_mask) | cacheattr;
+- } while ( (y = cmpxchg(&page->count_info, x, nx)) != x );
+-
+- if ( write )
+- put_page_type(page);
+- put_page(page);
+-
+- gdprintk(XENLOG_WARNING, "Error updating mappings for mfn %" PRI_mfn
+- " (pfn %" PRI_pfn ", from L1 entry %" PRIpte ") for d%d\n",
+- mfn, get_gpfn_from_mfn(mfn),
+- l1e_get_intpte(l1e), l1e_owner->domain_id);
+- return err;
+- }
++ if ( write )
++ put_page_type(page);
++ put_page(page);
++ gdprintk(XENLOG_WARNING,
++ "Attempt to change cache attributes of Xen heap page\n");
++ return -EACCES;
+ }
+
+ return 0;
+@@ -2467,25 +2412,10 @@ static int mod_l4_entry(l4_pgentry_t *pl4e,
+ */
+ static int cleanup_page_mappings(struct page_info *page)
+ {
+- unsigned int cacheattr =
+- (page->count_info & PGC_cacheattr_mask) >> PGC_cacheattr_base;
+ int rc = 0;
+ unsigned long mfn = mfn_x(page_to_mfn(page));
+
+ /*
+- * If we've modified xen mappings as a result of guest cache
+- * attributes, restore them to the "normal" state.
+- */
+- if ( unlikely(cacheattr) )
+- {
+- page->count_info &= ~PGC_cacheattr_mask;
+-
+- BUG_ON(is_special_page(page));
+-
+- rc = update_xen_mappings(mfn, 0);
+- }
+-
+- /*
+ * If this may be in a PV domain's IOMMU, remove it.
+ *
+ * NB that writable xenheap pages have their type set and cleared by
+diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
+index cb9052749963..8a9a43bb0a9d 100644
+--- a/xen/include/asm-x86/mm.h
++++ b/xen/include/asm-x86/mm.h
+@@ -69,25 +69,22 @@
+ /* Set when is using a page as a page table */
+ #define _PGC_page_table PG_shift(3)
+ #define PGC_page_table PG_mask(1, 3)
+- /* 3-bit PAT/PCD/PWT cache-attribute hint. */
+-#define PGC_cacheattr_base PG_shift(6)
+-#define PGC_cacheattr_mask PG_mask(7, 6)
+ /* Page is broken? */
+-#define _PGC_broken PG_shift(7)
+-#define PGC_broken PG_mask(1, 7)
++#define _PGC_broken PG_shift(4)
++#define PGC_broken PG_mask(1, 4)
+ /* Mutually-exclusive page states: { inuse, offlining, offlined, free }. */
+-#define PGC_state PG_mask(3, 9)
+-#define PGC_state_inuse PG_mask(0, 9)
+-#define PGC_state_offlining PG_mask(1, 9)
+-#define PGC_state_offlined PG_mask(2, 9)
+-#define PGC_state_free PG_mask(3, 9)
++#define PGC_state PG_mask(3, 6)
++#define PGC_state_inuse PG_mask(0, 6)
++#define PGC_state_offlining PG_mask(1, 6)
++#define PGC_state_offlined PG_mask(2, 6)
++#define PGC_state_free PG_mask(3, 6)
+ #define page_state_is(pg, st) (((pg)->count_info&PGC_state) == PGC_state_##st)
+ /* Page is not reference counted (see below for caveats) */
+-#define _PGC_extra PG_shift(10)
+-#define PGC_extra PG_mask(1, 10)
++#define _PGC_extra PG_shift(7)
++#define PGC_extra PG_mask(1, 7)
+
+ /* Count of references to this frame. */
+-#define PGC_count_width PG_shift(10)
++#define PGC_count_width PG_shift(7)
+ #define PGC_count_mask ((1UL<<PGC_count_width)-1)
+
+ /*
diff --git a/system/xen/xsa/xsa402-4.16-3.patch b/system/xen/xsa/xsa402-4.16-3.patch
new file mode 100644
index 000000000000..b4d2a4c835ae
--- /dev/null
+++ b/system/xen/xsa/xsa402-4.16-3.patch
@@ -0,0 +1,284 @@
+From: Andrew Cooper <andrew.cooper3@citrix.com>
+Subject: x86: Split cache_flush() out of cache_writeback()
+
+Subsequent changes will want a fully flushing version.
+
+Use the new helper rather than opencoding it in flush_area_local(). This
+resolves an outstanding issue where the conditional sfence is on the wrong
+side of the clflushopt loop. clflushopt is ordered with respect to older
+stores, not to younger stores.
+
+Rename gnttab_cache_flush()'s helper to avoid colliding in name.
+grant_table.c can see the prototype from cache.h so the build fails
+otherwise.
+
+This is part of XSA-402.
+
+Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
+Reviewed-by: Jan Beulich <jbeulich@suse.com>
+
+Xen 4.16 and earlier:
+ * Also backport half of c/s 3330013e67396 "VT-d / x86: re-arrange cache
+ syncing" to split cache_writeback() out of the IOMMU logic, but without the
+ associated hooks changes.
+
+diff --git a/xen/arch/x86/flushtlb.c b/xen/arch/x86/flushtlb.c
+index 25798df50f54..0c912b8669f8 100644
+--- a/xen/arch/x86/flushtlb.c
++++ b/xen/arch/x86/flushtlb.c
+@@ -234,7 +234,7 @@ unsigned int flush_area_local(const void *va, unsigned int flags)
+ if ( flags & FLUSH_CACHE )
+ {
+ const struct cpuinfo_x86 *c = &current_cpu_data;
+- unsigned long i, sz = 0;
++ unsigned long sz = 0;
+
+ if ( order < (BITS_PER_LONG - PAGE_SHIFT) )
+ sz = 1UL << (order + PAGE_SHIFT);
+@@ -244,13 +244,7 @@ unsigned int flush_area_local(const void *va, unsigned int flags)
+ c->x86_clflush_size && c->x86_cache_size && sz &&
+ ((sz >> 10) < c->x86_cache_size) )
+ {
+- alternative("", "sfence", X86_FEATURE_CLFLUSHOPT);
+- for ( i = 0; i < sz; i += c->x86_clflush_size )
+- alternative_input(".byte " __stringify(NOP_DS_PREFIX) ";"
+- " clflush %0",
+- "data16 clflush %0", /* clflushopt */
+- X86_FEATURE_CLFLUSHOPT,
+- "m" (((const char *)va)[i]));
++ cache_flush(va, sz);
+ flags &= ~FLUSH_CACHE;
+ }
+ else
+@@ -265,6 +259,80 @@ unsigned int flush_area_local(const void *va, unsigned int flags)
+ return flags;
+ }
+
++void cache_flush(const void *addr, unsigned int size)
++{
++ /*
++ * This function may be called before current_cpu_data is established.
++ * Hence a fallback is needed to prevent the loop below becoming infinite.
++ */
++ unsigned int clflush_size = current_cpu_data.x86_clflush_size ?: 16;
++ const void *end = addr + size;
++
++ addr -= (unsigned long)addr & (clflush_size - 1);
++ for ( ; addr < end; addr += clflush_size )
++ {
++ /*
++ * Note regarding the "ds" prefix use: it's faster to do a clflush
++ * + prefix than a clflush + nop, and hence the prefix is added instead
++ * of letting the alternative framework fill the gap by appending nops.
++ */
++ alternative_io("ds; clflush %[p]",
++ "data16 clflush %[p]", /* clflushopt */
++ X86_FEATURE_CLFLUSHOPT,
++ /* no outputs */,
++ [p] "m" (*(const char *)(addr)));
++ }
++
++ alternative("", "sfence", X86_FEATURE_CLFLUSHOPT);
++}
++
++void cache_writeback(const void *addr, unsigned int size)
++{
++ unsigned int clflush_size;
++ const void *end = addr + size;
++
++ /* Fall back to CLFLUSH{,OPT} when CLWB isn't available. */
++ if ( !boot_cpu_has(X86_FEATURE_CLWB) )
++ return cache_flush(addr, size);
++
++ /*
++ * This function may be called before current_cpu_data is established.
++ * Hence a fallback is needed to prevent the loop below becoming infinite.
++ */
++ clflush_size = current_cpu_data.x86_clflush_size ?: 16;
++ addr -= (unsigned long)addr & (clflush_size - 1);
++ for ( ; addr < end; addr += clflush_size )
++ {
++/*
++ * The arguments to a macro must not include preprocessor directives. Doing so
++ * results in undefined behavior, so we have to create some defines here in
++ * order to avoid it.
++ */
++#if defined(HAVE_AS_CLWB)
++# define CLWB_ENCODING "clwb %[p]"
++#elif defined(HAVE_AS_XSAVEOPT)
++# define CLWB_ENCODING "data16 xsaveopt %[p]" /* clwb */
++#else
++# define CLWB_ENCODING ".byte 0x66, 0x0f, 0xae, 0x30" /* clwb (%%rax) */
++#endif
++
++#define BASE_INPUT(addr) [p] "m" (*(const char *)(addr))
++#if defined(HAVE_AS_CLWB) || defined(HAVE_AS_XSAVEOPT)
++# define INPUT BASE_INPUT
++#else
++# define INPUT(addr) "a" (addr), BASE_INPUT(addr)
++#endif
++
++ asm volatile (CLWB_ENCODING :: INPUT(addr));
++
++#undef INPUT
++#undef BASE_INPUT
++#undef CLWB_ENCODING
++ }
++
++ asm volatile ("sfence" ::: "memory");
++}
++
+ unsigned int guest_flush_tlb_flags(const struct domain *d)
+ {
+ bool shadow = paging_mode_shadow(d);
+diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
+index 66f8ce71741c..4c742cd8fe81 100644
+--- a/xen/common/grant_table.c
++++ b/xen/common/grant_table.c
+@@ -3431,7 +3431,7 @@ gnttab_swap_grant_ref(XEN_GUEST_HANDLE_PARAM(gnttab_swap_grant_ref_t) uop,
+ return 0;
+ }
+
+-static int cache_flush(const gnttab_cache_flush_t *cflush, grant_ref_t *cur_ref)
++static int _cache_flush(const gnttab_cache_flush_t *cflush, grant_ref_t *cur_ref)
+ {
+ struct domain *d, *owner;
+ struct page_info *page;
+@@ -3525,7 +3525,7 @@ gnttab_cache_flush(XEN_GUEST_HANDLE_PARAM(gnttab_cache_flush_t) uop,
+ return -EFAULT;
+ for ( ; ; )
+ {
+- int ret = cache_flush(&op, cur_ref);
++ int ret = _cache_flush(&op, cur_ref);
+
+ if ( ret < 0 )
+ return ret;
+diff --git a/xen/drivers/passthrough/vtd/extern.h b/xen/drivers/passthrough/vtd/extern.h
+index 01e010a10d61..401079299725 100644
+--- a/xen/drivers/passthrough/vtd/extern.h
++++ b/xen/drivers/passthrough/vtd/extern.h
+@@ -76,7 +76,6 @@ int __must_check qinval_device_iotlb_sync(struct vtd_iommu *iommu,
+ struct pci_dev *pdev,
+ u16 did, u16 size, u64 addr);
+
+-unsigned int get_cache_line_size(void);
+ void flush_all_cache(void);
+
+ uint64_t alloc_pgtable_maddr(unsigned long npages, nodeid_t node);
+diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c
+index 8975c1de61bc..bc377c9bcfa4 100644
+--- a/xen/drivers/passthrough/vtd/iommu.c
++++ b/xen/drivers/passthrough/vtd/iommu.c
+@@ -31,6 +31,7 @@
+ #include <xen/pci.h>
+ #include <xen/pci_regs.h>
+ #include <xen/keyhandler.h>
++#include <asm/cache.h>
+ #include <asm/msi.h>
+ #include <asm/nops.h>
+ #include <asm/irq.h>
+@@ -206,54 +207,6 @@ static void check_cleanup_domid_map(const struct domain *d,
+ }
+ }
+
+-static void sync_cache(const void *addr, unsigned int size)
+-{
+- static unsigned long clflush_size = 0;
+- const void *end = addr + size;
+-
+- if ( clflush_size == 0 )
+- clflush_size = get_cache_line_size();
+-
+- addr -= (unsigned long)addr & (clflush_size - 1);
+- for ( ; addr < end; addr += clflush_size )
+-/*
+- * The arguments to a macro must not include preprocessor directives. Doing so
+- * results in undefined behavior, so we have to create some defines here in
+- * order to avoid it.
+- */
+-#if defined(HAVE_AS_CLWB)
+-# define CLWB_ENCODING "clwb %[p]"
+-#elif defined(HAVE_AS_XSAVEOPT)
+-# define CLWB_ENCODING "data16 xsaveopt %[p]" /* clwb */
+-#else
+-# define CLWB_ENCODING ".byte 0x66, 0x0f, 0xae, 0x30" /* clwb (%%rax) */
+-#endif
+-
+-#define BASE_INPUT(addr) [p] "m" (*(const char *)(addr))
+-#if defined(HAVE_AS_CLWB) || defined(HAVE_AS_XSAVEOPT)
+-# define INPUT BASE_INPUT
+-#else
+-# define INPUT(addr) "a" (addr), BASE_INPUT(addr)
+-#endif
+- /*
+- * Note regarding the use of NOP_DS_PREFIX: it's faster to do a clflush
+- * + prefix than a clflush + nop, and hence the prefix is added instead
+- * of letting the alternative framework fill the gap by appending nops.
+- */
+- alternative_io_2(".byte " __stringify(NOP_DS_PREFIX) "; clflush %[p]",
+- "data16 clflush %[p]", /* clflushopt */
+- X86_FEATURE_CLFLUSHOPT,
+- CLWB_ENCODING,
+- X86_FEATURE_CLWB, /* no outputs */,
+- INPUT(addr));
+-#undef INPUT
+-#undef BASE_INPUT
+-#undef CLWB_ENCODING
+-
+- alternative_2("", "sfence", X86_FEATURE_CLFLUSHOPT,
+- "sfence", X86_FEATURE_CLWB);
+-}
+-
+ /* Allocate page table, return its machine address */
+ uint64_t alloc_pgtable_maddr(unsigned long npages, nodeid_t node)
+ {
+@@ -273,7 +226,7 @@ uint64_t alloc_pgtable_maddr(unsigned long npages, nodeid_t node)
+ clear_page(vaddr);
+
+ if ( (iommu_ops.init ? &iommu_ops : &vtd_ops)->sync_cache )
+- sync_cache(vaddr, PAGE_SIZE);
++ cache_writeback(vaddr, PAGE_SIZE);
+ unmap_domain_page(vaddr);
+ cur_pg++;
+ }
+@@ -1305,7 +1258,7 @@ int __init iommu_alloc(struct acpi_drhd_unit *drhd)
+ iommu->nr_pt_levels = agaw_to_level(agaw);
+
+ if ( !ecap_coherent(iommu->ecap) )
+- vtd_ops.sync_cache = sync_cache;
++ vtd_ops.sync_cache = cache_writeback;
+
+ /* allocate domain id bitmap */
+ iommu->domid_bitmap = xzalloc_array(unsigned long, BITS_TO_LONGS(nr_dom));
+diff --git a/xen/drivers/passthrough/vtd/x86/vtd.c b/xen/drivers/passthrough/vtd/x86/vtd.c
+index 6681dccd6970..55f0faa521cb 100644
+--- a/xen/drivers/passthrough/vtd/x86/vtd.c
++++ b/xen/drivers/passthrough/vtd/x86/vtd.c
+@@ -47,11 +47,6 @@ void unmap_vtd_domain_page(const void *va)
+ unmap_domain_page(va);
+ }
+
+-unsigned int get_cache_line_size(void)
+-{
+- return ((cpuid_ebx(1) >> 8) & 0xff) * 8;
+-}
+-
+ void flush_all_cache()
+ {
+ wbinvd();
+diff --git a/xen/include/asm-x86/cache.h b/xen/include/asm-x86/cache.h
+index 1f7173d8c72c..e4770efb22b9 100644
+--- a/xen/include/asm-x86/cache.h
++++ b/xen/include/asm-x86/cache.h
+@@ -11,4 +11,11 @@
+
+ #define __read_mostly __section(".data.read_mostly")
+
++#ifndef __ASSEMBLY__
++
++void cache_flush(const void *addr, unsigned int size);
++void cache_writeback(const void *addr, unsigned int size);
++
++#endif
++
+ #endif
diff --git a/system/xen/xsa/xsa402-4.16-4.patch b/system/xen/xsa/xsa402-4.16-4.patch
new file mode 100644
index 000000000000..21109225d7d7
--- /dev/null
+++ b/system/xen/xsa/xsa402-4.16-4.patch
@@ -0,0 +1,83 @@
+From: Andrew Cooper <andrew.cooper3@citrix.com>
+Subject: x86/amd: Work around CLFLUSH ordering on older parts
+
+On pre-CLFLUSHOPT AMD CPUs, CLFLUSH is weakely ordered with everything,
+including reads and writes to the address, and LFENCE/SFENCE instructions.
+
+This creates a multitude of problematic corner cases, laid out in the manual.
+Arrange to use MFENCE on both sides of the CLFLUSH to force proper ordering.
+
+This is part of XSA-402.
+
+Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
+Reviewed-by: Jan Beulich <jbeulich@suse.com>
+
+diff --git a/xen/arch/x86/cpu/amd.c b/xen/arch/x86/cpu/amd.c
+index a8e37dbb1f5c..b3b9a0df5fed 100644
+--- a/xen/arch/x86/cpu/amd.c
++++ b/xen/arch/x86/cpu/amd.c
+@@ -812,6 +812,14 @@ static void init_amd(struct cpuinfo_x86 *c)
+ if (!cpu_has_lfence_dispatch)
+ __set_bit(X86_FEATURE_MFENCE_RDTSC, c->x86_capability);
+
++ /*
++ * On pre-CLFLUSHOPT AMD CPUs, CLFLUSH is weakly ordered with
++ * everything, including reads and writes to address, and
++ * LFENCE/SFENCE instructions.
++ */
++ if (!cpu_has_clflushopt)
++ setup_force_cpu_cap(X86_BUG_CLFLUSH_MFENCE);
++
+ switch(c->x86)
+ {
+ case 0xf ... 0x11:
+diff --git a/xen/arch/x86/flushtlb.c b/xen/arch/x86/flushtlb.c
+index 0c912b8669f8..dcbb4064012e 100644
+--- a/xen/arch/x86/flushtlb.c
++++ b/xen/arch/x86/flushtlb.c
+@@ -259,6 +259,13 @@ unsigned int flush_area_local(const void *va, unsigned int flags)
+ return flags;
+ }
+
++/*
++ * On pre-CLFLUSHOPT AMD CPUs, CLFLUSH is weakly ordered with everything,
++ * including reads and writes to address, and LFENCE/SFENCE instructions.
++ *
++ * This function only works safely after alternatives have run. Luckily, at
++ * the time of writing, we don't flush the caches that early.
++ */
+ void cache_flush(const void *addr, unsigned int size)
+ {
+ /*
+@@ -268,6 +275,8 @@ void cache_flush(const void *addr, unsigned int size)
+ unsigned int clflush_size = current_cpu_data.x86_clflush_size ?: 16;
+ const void *end = addr + size;
+
++ alternative("", "mfence", X86_BUG_CLFLUSH_MFENCE);
++
+ addr -= (unsigned long)addr & (clflush_size - 1);
+ for ( ; addr < end; addr += clflush_size )
+ {
+@@ -283,7 +292,9 @@ void cache_flush(const void *addr, unsigned int size)
+ [p] "m" (*(const char *)(addr)));
+ }
+
+- alternative("", "sfence", X86_FEATURE_CLFLUSHOPT);
++ alternative_2("",
++ "sfence", X86_FEATURE_CLFLUSHOPT,
++ "mfence", X86_BUG_CLFLUSH_MFENCE);
+ }
+
+ void cache_writeback(const void *addr, unsigned int size)
+diff --git a/xen/include/asm-x86/cpufeatures.h b/xen/include/asm-x86/cpufeatures.h
+index 7413febd7ad8..ff3157d52d13 100644
+--- a/xen/include/asm-x86/cpufeatures.h
++++ b/xen/include/asm-x86/cpufeatures.h
+@@ -47,6 +47,7 @@ XEN_CPUFEATURE(XEN_IBT, X86_SYNTH(27)) /* Xen uses CET Indirect Branch
+
+ #define X86_BUG_FPU_PTRS X86_BUG( 0) /* (F)X{SAVE,RSTOR} doesn't save/restore FOP/FIP/FDP. */
+ #define X86_BUG_NULL_SEG X86_BUG( 1) /* NULL-ing a selector preserves the base and limit. */
++#define X86_BUG_CLFLUSH_MFENCE X86_BUG( 2) /* MFENCE needed to serialise CLFLUSH */
+
+ /* Total number of capability words, inc synth and bug words. */
+ #define NCAPINTS (FSCAPINTS + X86_NR_SYNTH + X86_NR_BUG) /* N 32-bit words worth of info */
diff --git a/system/xen/xsa/xsa402-4.16-5.patch b/system/xen/xsa/xsa402-4.16-5.patch
new file mode 100644
index 000000000000..4806d25c6fa5
--- /dev/null
+++ b/system/xen/xsa/xsa402-4.16-5.patch
@@ -0,0 +1,148 @@
+From: Andrew Cooper <andrew.cooper3@citrix.com>
+Subject: x86/pv: Track and flush non-coherent mappings of RAM
+
+There are legitimate uses of WC mappings of RAM, e.g. for DMA buffers with
+devices that make non-coherent writes. The Linux sound subsystem makes
+extensive use of this technique.
+
+For such usecases, the guest's DMA buffer is mapped and consistently used as
+WC, and Xen doesn't interact with the buffer.
+
+However, a mischevious guest can use WC mappings to deliberately create
+non-coherency between the cache and RAM, and use this to trick Xen into
+validating a pagetable which isn't actually safe.
+
+Allocate a new PGT_non_coherent to track the non-coherency of mappings. Set
+it whenever a non-coherent writeable mapping is created. If the page is used
+as anything other than PGT_writable_page, force a cache flush before
+validation. Also force a cache flush before the page is returned to the heap.
+
+This is CVE-2022-26364, part of XSA-402.
+
+Reported-by: Jann Horn <jannh@google.com>
+Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
+Reviewed-by: George Dunlap <george.dunlap@citrix.com>
+Reviewed-by: Jan Beulich <jbeulich@suse.com>
+
+diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
+index ab32d13a1a0d..bab9624fabb7 100644
+--- a/xen/arch/x86/mm.c
++++ b/xen/arch/x86/mm.c
+@@ -997,6 +997,15 @@ get_page_from_l1e(
+ return -EACCES;
+ }
+
++ /*
++ * Track writeable non-coherent mappings to RAM pages, to trigger a cache
++ * flush later if the target is used as anything but a PGT_writeable page.
++ * We care about all writeable mappings, including foreign mappings.
++ */
++ if ( !boot_cpu_has(X86_FEATURE_XEN_SELFSNOOP) &&
++ (l1f & (PAGE_CACHE_ATTRS | _PAGE_RW)) == (_PAGE_WC | _PAGE_RW) )
++ set_bit(_PGT_non_coherent, &page->u.inuse.type_info);
++
+ return 0;
+
+ could_not_pin:
+@@ -2454,6 +2463,19 @@ static int cleanup_page_mappings(struct page_info *page)
+ }
+ }
+
++ /*
++ * Flush the cache if there were previously non-coherent writeable
++ * mappings of this page. This forces the page to be coherent before it
++ * is freed back to the heap.
++ */
++ if ( __test_and_clear_bit(_PGT_non_coherent, &page->u.inuse.type_info) )
++ {
++ void *addr = __map_domain_page(page);
++
++ cache_flush(addr, PAGE_SIZE);
++ unmap_domain_page(addr);
++ }
++
+ return rc;
+ }
+
+@@ -3028,6 +3050,22 @@ static int _get_page_type(struct page_info *page, unsigned long type,
+ if ( unlikely(!(nx & PGT_validated)) )
+ {
+ /*
++ * Flush the cache if there were previously non-coherent mappings of
++ * this page, and we're trying to use it as anything other than a
++ * writeable page. This forces the page to be coherent before we
++ * validate its contents for safety.
++ */
++ if ( (nx & PGT_non_coherent) && type != PGT_writable_page )
++ {
++ void *addr = __map_domain_page(page);
++
++ cache_flush(addr, PAGE_SIZE);
++ unmap_domain_page(addr);
++
++ page->u.inuse.type_info &= ~PGT_non_coherent;
++ }
++
++ /*
+ * No special validation needed for writable or shared pages. Page
+ * tables and GDT/LDT need to have their contents audited.
+ *
+diff --git a/xen/arch/x86/pv/grant_table.c b/xen/arch/x86/pv/grant_table.c
+index 0325618c9883..81c72e61ed55 100644
+--- a/xen/arch/x86/pv/grant_table.c
++++ b/xen/arch/x86/pv/grant_table.c
+@@ -109,7 +109,17 @@ int create_grant_pv_mapping(uint64_t addr, mfn_t frame,
+
+ ol1e = *pl1e;
+ if ( UPDATE_ENTRY(l1, pl1e, ol1e, nl1e, gl1mfn, curr, 0) )
++ {
++ /*
++ * We always create mappings in this path. However, our caller,
++ * map_grant_ref(), only passes potentially non-zero cache_flags for
++ * MMIO frames, so this path doesn't create non-coherent mappings of
++ * RAM frames and there's no need to calculate PGT_non_coherent.
++ */
++ ASSERT(!cache_flags || is_iomem_page(frame));
++
+ rc = GNTST_okay;
++ }
+
+ out_unlock:
+ page_unlock(page);
+@@ -294,7 +304,18 @@ int replace_grant_pv_mapping(uint64_t addr, mfn_t frame,
+ l1e_get_flags(ol1e), addr, grant_pte_flags);
+
+ if ( UPDATE_ENTRY(l1, pl1e, ol1e, nl1e, gl1mfn, curr, 0) )
++ {
++ /*
++ * Generally, replace_grant_pv_mapping() is used to destroy mappings
++ * (n1le = l1e_empty()), but it can be a present mapping on the
++ * GNTABOP_unmap_and_replace path.
++ *
++ * In such cases, the PTE is fully transplanted from its old location
++ * via steal_linear_addr(), so we need not perform PGT_non_coherent
++ * checking here.
++ */
+ rc = GNTST_okay;
++ }
+
+ out_unlock:
+ page_unlock(page);
+diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
+index 8a9a43bb0a9d..7464167ae192 100644
+--- a/xen/include/asm-x86/mm.h
++++ b/xen/include/asm-x86/mm.h
+@@ -53,8 +53,12 @@
+ #define _PGT_partial PG_shift(8)
+ #define PGT_partial PG_mask(1, 8)
+
++/* Has this page been mapped writeable with a non-coherent memory type? */
++#define _PGT_non_coherent PG_shift(9)
++#define PGT_non_coherent PG_mask(1, 9)
++
+ /* Count of uses of this frame as its current type. */
+-#define PGT_count_width PG_shift(8)
++#define PGT_count_width PG_shift(9)
+ #define PGT_count_mask ((1UL<<PGT_count_width)-1)
+
+ /* Are the 'type mask' bits identical? */
generated by cgit v1.2.3 (git 2.26.2) at 2024-11-19 05:46:01 +0000