From b0182e537e5aba38031a5009cb16d5e924342458 Mon Sep 17 00:00:00 2001 From: Steve Sistare Date: Wed, 7 Jun 2023 08:18:36 -0700 Subject: [PATCH] exec/memory: Introduce RAM_NAMED_FILE flag MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit migrate_ignore_shared() is an optimization that avoids copying memory that is visible and can be mapped on the target. However, a memory-backend-ram or a memory-backend-memfd block with the RAM_SHARED flag set is not migrated when migrate_ignore_shared() is true. This is wrong, because the block has no named backing store, and its contents will be lost. To fix, ignore shared memory iff it is a named file. Define a new flag RAM_NAMED_FILE to distinguish this case. Signed-off-by: Steve Sistare Reviewed-by: Peter Xu Message-Id: <1686151116-253260-1-git-send-email-steven.sistare@oracle.com> Signed-off-by: Philippe Mathieu-Daudé --- backends/hostmem-file.c | 1 + include/exec/cpu-common.h | 1 + include/exec/memory.h | 3 +++ migration/ram.c | 3 ++- qapi/migration.json | 4 ++-- softmmu/physmem.c | 7 ++++++- 6 files changed, 15 insertions(+), 4 deletions(-) diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c index 38ea65bec5..b4335a80e6 100644 --- a/backends/hostmem-file.c +++ b/backends/hostmem-file.c @@ -57,6 +57,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) ram_flags = backend->share ? RAM_SHARED : 0; ram_flags |= backend->reserve ? 0 : RAM_NORESERVE; ram_flags |= fb->is_pmem ? RAM_PMEM : 0; + ram_flags |= RAM_NAMED_FILE; memory_region_init_ram_from_file(&backend->mr, OBJECT(backend), name, backend->size, fb->align, ram_flags, fb->mem_path, fb->offset, fb->readonly, diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h index e5a55ede5f..87dc9a752c 100644 --- a/include/exec/cpu-common.h +++ b/include/exec/cpu-common.h @@ -93,6 +93,7 @@ void qemu_ram_set_uf_zeroable(RAMBlock *rb); bool qemu_ram_is_migratable(RAMBlock *rb); void qemu_ram_set_migratable(RAMBlock *rb); void qemu_ram_unset_migratable(RAMBlock *rb); +bool qemu_ram_is_named_file(RAMBlock *rb); int qemu_ram_get_fd(RAMBlock *rb); size_t qemu_ram_pagesize(RAMBlock *block); diff --git a/include/exec/memory.h b/include/exec/memory.h index c3661b2276..47c2e0221c 100644 --- a/include/exec/memory.h +++ b/include/exec/memory.h @@ -232,6 +232,9 @@ typedef struct IOMMUTLBEvent { /* RAM that isn't accessible through normal means. */ #define RAM_PROTECTED (1 << 8) +/* RAM is an mmap-ed named file */ +#define RAM_NAMED_FILE (1 << 9) + static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn, IOMMUNotifierFlag flags, hwaddr start, hwaddr end, diff --git a/migration/ram.c b/migration/ram.c index 88a6c82e63..5283a75f02 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -197,7 +197,8 @@ static bool postcopy_preempt_active(void) bool ramblock_is_ignored(RAMBlock *block) { return !qemu_ram_is_migratable(block) || - (migrate_ignore_shared() && qemu_ram_is_shared(block)); + (migrate_ignore_shared() && qemu_ram_is_shared(block) + && qemu_ram_is_named_file(block)); } #undef RAMBLOCK_FOREACH diff --git a/qapi/migration.json b/qapi/migration.json index 179af0c4d8..5bb5ab82a0 100644 --- a/qapi/migration.json +++ b/qapi/migration.json @@ -465,8 +465,8 @@ # block devices (and thus take locks) immediately at the end of # migration. (since 3.0) # -# @x-ignore-shared: If enabled, QEMU will not migrate shared memory -# (since 4.0) +# @x-ignore-shared: If enabled, QEMU will not migrate shared memory that is +# accessible on the destination machine. (since 4.0) # # @validate-uuid: Send the UUID of the source to allow the destination # to ensure it is the same. (since 4.2) diff --git a/softmmu/physmem.c b/softmmu/physmem.c index 588d0d166b..6bdd944fe8 100644 --- a/softmmu/physmem.c +++ b/softmmu/physmem.c @@ -1570,6 +1570,11 @@ void qemu_ram_unset_migratable(RAMBlock *rb) rb->flags &= ~RAM_MIGRATABLE; } +bool qemu_ram_is_named_file(RAMBlock *rb) +{ + return rb->flags & RAM_NAMED_FILE; +} + int qemu_ram_get_fd(RAMBlock *rb) { return rb->fd; @@ -1880,7 +1885,7 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, /* Just support these ram flags by now. */ assert((ram_flags & ~(RAM_SHARED | RAM_PMEM | RAM_NORESERVE | - RAM_PROTECTED)) == 0); + RAM_PROTECTED | RAM_NAMED_FILE)) == 0); if (xen_enabled()) { error_setg(errp, "-mem-path not supported with Xen");