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physmem: preserve ram blocks for cpr

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Save the memfd for ramblocks in CPR state, along with a name that
uniquely identifies it.  The block's idstr is not yet set, so it
cannot be used for this purpose.  Find the saved memfd in new QEMU when
creating a block.  If size of a resizable block is larger in new QEMU,
extend it via the file_ram_alloc truncate parameter, and the extra space
will be usable after a guest reset.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/1736967650-129648-9-git-send-email-steven.sistare@oracle.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
This commit is contained in:
Steve Sistare 2025-01-15 11:00:34 -08:00 • committed by Fabiano Rosas
parent e7d79011a4
commit 2b7e9739fa
1 changed files with 39 additions and 5 deletions
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44
system/physmem.c
View file

@ -70,6 +70,7 @@
#include "qemu/pmem.h"
#include "migration/cpr.h"
#include "migration/vmstate.h"
#include "qemu/range.h"
@ -1661,6 +1662,18 @@ void qemu_ram_unset_idstr(RAMBlock *block)
}
}
static char *cpr_name(MemoryRegion *mr)
{
const char *mr_name = memory_region_name(mr);
g_autofree char *id = mr->dev ? qdev_get_dev_path(mr->dev) : NULL;
if (id) {
return g_strdup_printf("%s/%s", id, mr_name);
} else {
return g_strdup(mr_name);
}
}
size_t qemu_ram_pagesize(RAMBlock *rb)
{
return rb->page_size;
@ -2080,15 +2093,25 @@ RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr,
* shared with another process if CPR is being used. Use memfd if available
* because it has no size limits, else use POSIX shm.
*/
static int qemu_ram_get_shared_fd(const char *name, Error **errp)
static int qemu_ram_get_shared_fd(const char *name, bool *reused, Error **errp)
{
int fd;
int fd = cpr_find_fd(name, 0);
if (fd >= 0) {
*reused = true;
return fd;
}
if (qemu_memfd_check(0)) {
fd = qemu_memfd_create(name, 0, 0, 0, 0, errp);
} else {
fd = qemu_shm_alloc(0, errp);
}
if (fd >= 0) {
cpr_save_fd(name, 0, fd);
}
*reused = false;
return fd;
}
#endif
@ -2118,8 +2141,9 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
ram_flags |= RAM_SHARED;
}
if (ram_flags & RAM_SHARED) {
const char *name = memory_region_name(mr);
int fd = qemu_ram_get_shared_fd(name, errp);
bool reused;
g_autofree char *name = cpr_name(mr);
int fd = qemu_ram_get_shared_fd(name, &reused, errp);
if (fd < 0) {
return NULL;
@ -2133,9 +2157,14 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
* fd is not supported, but previous QEMU versions that called
* qemu_anon_ram_alloc for anonymous shared memory could have
* succeeded. Quietly fail and fall back.
*
* After cpr-transfer, new QEMU could create a memory region
* with a larger max size than old, so pass reused to grow the
* region if necessary. The extra space will be usable after a
* guest reset.
*/
new_block = qemu_ram_alloc_from_fd(size, max_size, resized, mr,
ram_flags, fd, 0, false, NULL);
ram_flags, fd, 0, reused, NULL);
if (new_block) {
trace_qemu_ram_alloc_shared(name, new_block->used_length,
new_block->max_length, fd,
@ -2143,6 +2172,7 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
return new_block;
}
cpr_delete_fd(name, 0);
close(fd);
/* fall back to anon allocation */
}
@ -2221,6 +2251,8 @@ static void reclaim_ramblock(RAMBlock *block)
void qemu_ram_free(RAMBlock *block)
{
g_autofree char *name = NULL;
if (!block) {
return;
}
@ -2231,6 +2263,8 @@ void qemu_ram_free(RAMBlock *block)
}
qemu_mutex_lock_ramlist();
name = cpr_name(block->mr);
cpr_delete_fd(name, 0);
QLIST_REMOVE_RCU(block, next);
ram_list.mru_block = NULL;
/* Write list before version */