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exec/memory: Introduce RAM_NAMED_FILE flag

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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 <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Message-Id: <1686151116-253260-1-git-send-email-steven.sistare@oracle.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
This commit is contained in:
Steve Sistare 2023-06-07 08:18:36 -07:00 committed by Philippe Mathieu-Daudé
parent 6fe4f6c941
commit b0182e537e
6 changed files with 15 additions and 4 deletions
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1
backends/hostmem-file.c
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@ -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,

1
include/exec/cpu-common.h
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@ -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);

3
include/exec/memory.h
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@ -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,

3
migration/ram.c
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@ -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

4
qapi/migration.json
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@ -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)

7
softmmu/physmem.c
View File

@ -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");