Merge branch 'xenfv-kvm-15' of git://git.infradead.org/users/dwmw2/qemu into HEAD

This adds support for emulating Xen under Linux/KVM, based on kernel
patches which have been present since Linux v5.12. As with the kernel
support, it's derived from work started by João Martins of Oracle in
2018.

This series just adds the basic platform support — CPUID, hypercalls,
event channels, a stub of XenStore.

A full single-tenant internal implementation of XenStore, and patches
to make QEMU's Xen PV drivers work with this Xen emulation, are waiting
in the wings to be submitted in a follow-on patch series.

As noted in the documentation, it's enabled by setting the xen-version
property on the KVM accelerator, e.g.:

 qemu-system-x86_64 -serial mon:stdio -M q35 -display none -m 1G -smp 2 \
    -accel kvm,xen-version=0x4000e,kernel-irqchip=split \
    -kernel vmlinuz-6.0.7-301.fc37.x86_64 \
    -append "console=ttyS0 root=/dev/sda1" \
    -drive file=/var/lib/libvirt/images/fedora28.qcow2,if=none,id=disk \
    -device ahci,id=ahci -device ide-hd,drive=disk,bus=ahci.0

Even before this was merged, we've already been using it to find and fix
bugs in the Linux kernel Xen guest support:

https://lore.kernel.org/all/4bffa69a949bfdc92c4a18e5a1c3cbb3b94a0d32.camel@infradead.org/
https://lore.kernel.org/all/871qnunycr.ffs@tglx/

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 93 insertions, 1 deletions

diff --git a/include/hw/xen/interface/io/netif.h b/include/hw/xen/interface/io/netif.h
index 48fa530950..00dd258712 100644
--- a/include/hw/xen/interface/io/netif.h
+++ b/include/hw/xen/interface/io/netif.h
@@ -171,7 +171,7 @@
  * The ability of the backend to use a control ring is advertised by
  * setting:
  *
- * /local/domain/X/backend/<domid>/<vif>/feature-ctrl-ring = "1"
+ * /local/domain/X/backend/vif/<domid>/<vif>/feature-ctrl-ring = "1"
  *
  * The frontend provides a control ring to the backend by setting:
  *
@@ -191,6 +191,32 @@
  */
 
 /*
+ * Link state
+ * ==========
+ *
+ * The backend can advertise its current link (carrier) state to the
+ * frontend using the /local/domain/X/backend/vif/<domid>/<vif>/carrier
+ * node. If this node is not present, then the frontend should assume that
+ * the link is up (for compatibility with backends that do not implement
+ * this feature). If this node is present, then a value of "0" should be
+ * interpreted by the frontend as the link being down (no carrier) and a
+ * value of "1" should be interpreted as the link being up (carrier
+ * present).
+ */
+
+/*
+ * MTU
+ * ===
+ *
+ * The toolstack may set a value of MTU for the frontend by setting the
+ * /local/domain/<domid>/device/vif/<vif>/mtu node with the MTU value in
+ * octets. If this node is absent the frontend should assume an MTU value
+ * of 1500 octets. A frontend is also at liberty to ignore this value so
+ * it is only suitable for informing the frontend that a packet payload
+ * >1500 octets is permitted.
+ */
+
+/*
  * Hash types
  * ==========
  *
@@ -268,6 +294,62 @@
 #define XEN_NETIF_CTRL_HASH_ALGORITHM_TOEPLITZ 1
 
 /*
+ * This algorithm uses a 'key' as well as the data buffer itself.
+ * (Buffer[] and Key[] are treated as shift-registers where the MSB of
+ * Buffer/Key[0] is considered 'left-most' and the LSB of Buffer/Key[N-1]
+ * is the 'right-most').
+ *
+ * Value = 0
+ * For number of bits in Buffer[]
+ *    If (left-most bit of Buffer[] is 1)
+ *        Value ^= left-most 32 bits of Key[]
+ *    Key[] << 1
+ *    Buffer[] << 1
+ *
+ * The code below is provided for convenience where an operating system
+ * does not already provide an implementation.
+ */
+#ifdef XEN_NETIF_DEFINE_TOEPLITZ
+static uint32_t xen_netif_toeplitz_hash(const uint8_t *key,
+                                        unsigned int keylen,
+                                        const uint8_t *buf,
+                                        unsigned int buflen)
+{
+    unsigned int keyi, bufi;
+    uint64_t prefix = 0;
+    uint64_t hash = 0;
+
+    /* Pre-load prefix with the first 8 bytes of the key */
+    for (keyi = 0; keyi < 8; keyi++) {
+        prefix <<= 8;
+        prefix |= (keyi < keylen) ? key[keyi] : 0;
+    }
+
+    for (bufi = 0; bufi < buflen; bufi++) {
+        uint8_t byte = buf[bufi];
+        unsigned int bit;
+
+        for (bit = 0; bit < 8; bit++) {
+            if (byte & 0x80)
+                hash ^= prefix;
+            prefix <<= 1;
+            byte <<=1;
+        }
+
+        /*
+         * 'prefix' has now been left-shifted by 8, so
+         * OR in the next byte.
+         */
+        prefix |= (keyi < keylen) ? key[keyi] : 0;
+        keyi++;
+    }
+
+    /* The valid part of the hash is in the upper 32 bits. */
+    return hash >> 32;
+}
+#endif /* XEN_NETIF_DEFINE_TOEPLITZ */
+
+/*
  * Control requests (struct xen_netif_ctrl_request)
  * ================================================
  *
@@ -1008,3 +1090,13 @@ DEFINE_RING_TYPES(netif_rx, struct netif_rx_request, struct netif_rx_response);
 #define NETIF_RSP_NULL             1
 
 #endif
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */