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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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7
softmmu/physmem.c
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@ -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");