diff options
| -rw-r--r-- | include/exec/ramblock.h | 10 | ||||
| -rw-r--r-- | migration/postcopy-ram.c | 15 | ||||
| -rw-r--r-- | migration/ram.c | 11 |
3 files changed, 31 insertions, 5 deletions
diff --git a/include/exec/ramblock.h b/include/exec/ramblock.h index 07d50864d8..664701b759 100644 --- a/include/exec/ramblock.h +++ b/include/exec/ramblock.h @@ -59,6 +59,16 @@ struct RAMBlock { */ unsigned long *clear_bmap; uint8_t clear_bmap_shift; + + /* + * RAM block length that corresponds to the used_length on the migration + * source (after RAM block sizes were synchronized). Especially, after + * starting to run the guest, used_length and postcopy_length can differ. + * Used to register/unregister uffd handlers and as the size of the received + * bitmap. Receiving any page beyond this length will bail out, as it + * could not have been valid on the source. + */ + ram_addr_t postcopy_length; }; #endif #endif diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c index ab482adef1..2e9697bdd2 100644 --- a/migration/postcopy-ram.c +++ b/migration/postcopy-ram.c @@ -17,6 +17,7 @@ */ #include "qemu/osdep.h" +#include "qemu/rcu.h" #include "exec/target_page.h" #include "migration.h" #include "qemu-file.h" @@ -30,6 +31,7 @@ #include "qemu/error-report.h" #include "trace.h" #include "hw/boards.h" +#include "exec/ramblock.h" /* Arbitrary limit on size of each discard command, * keeps them around ~200 bytes @@ -453,6 +455,13 @@ static int init_range(RAMBlock *rb, void *opaque) trace_postcopy_init_range(block_name, host_addr, offset, length); /* + * Save the used_length before running the guest. In case we have to + * resize RAM blocks when syncing RAM block sizes from the source during + * precopy, we'll update it manually via the ram block notifier. + */ + rb->postcopy_length = length; + + /* * We need the whole of RAM to be truly empty for postcopy, so things * like ROMs and any data tables built during init must be zero'd * - we're going to get the copy from the source anyway. @@ -474,7 +483,7 @@ static int cleanup_range(RAMBlock *rb, void *opaque) const char *block_name = qemu_ram_get_idstr(rb); void *host_addr = qemu_ram_get_host_addr(rb); ram_addr_t offset = qemu_ram_get_offset(rb); - ram_addr_t length = qemu_ram_get_used_length(rb); + ram_addr_t length = rb->postcopy_length; MigrationIncomingState *mis = opaque; struct uffdio_range range_struct; trace_postcopy_cleanup_range(block_name, host_addr, offset, length); @@ -580,7 +589,7 @@ static int nhp_range(RAMBlock *rb, void *opaque) const char *block_name = qemu_ram_get_idstr(rb); void *host_addr = qemu_ram_get_host_addr(rb); ram_addr_t offset = qemu_ram_get_offset(rb); - ram_addr_t length = qemu_ram_get_used_length(rb); + ram_addr_t length = rb->postcopy_length; trace_postcopy_nhp_range(block_name, host_addr, offset, length); /* @@ -624,7 +633,7 @@ static int ram_block_enable_notify(RAMBlock *rb, void *opaque) struct uffdio_register reg_struct; reg_struct.range.start = (uintptr_t)qemu_ram_get_host_addr(rb); - reg_struct.range.len = qemu_ram_get_used_length(rb); + reg_struct.range.len = rb->postcopy_length; reg_struct.mode = UFFDIO_REGISTER_MODE_MISSING; /* Now tell our userfault_fd that it's responsible for this area */ diff --git a/migration/ram.c b/migration/ram.c index 26ed42b87d..6d09ca78bc 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -240,7 +240,7 @@ int64_t ramblock_recv_bitmap_send(QEMUFile *file, return -1; } - nbits = block->used_length >> TARGET_PAGE_BITS; + nbits = block->postcopy_length >> TARGET_PAGE_BITS; /* * Make sure the tmp bitmap buffer is big enough, e.g., on 32bit @@ -3530,7 +3530,13 @@ static int ram_load_postcopy(QEMUFile *f) break; } - if (!offset_in_ramblock(block, addr)) { + /* + * Relying on used_length is racy and can result in false positives. + * We might place pages beyond used_length in case RAM was shrunk + * while in postcopy, which is fine - trying to place via + * UFFDIO_COPY/UFFDIO_ZEROPAGE will never segfault. + */ + if (!block->host || addr >= block->postcopy_length) { error_report("Illegal RAM offset " RAM_ADDR_FMT, addr); ret = -EINVAL; break; @@ -4143,6 +4149,7 @@ static void ram_mig_ram_block_resized(RAMBlockNotifier *n, void *host, rb->idstr); } } + rb->postcopy_length = new_size; break; case POSTCOPY_INCOMING_NONE: case POSTCOPY_INCOMING_RUNNING: |