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system/physmem: poisoned memory discard on reboot

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Repair poisoned memory location(s), calling ram_block_discard_range():
punching a hole in the backend file when necessary and regenerating
a usable memory.
If the kernel doesn't support the madvise calls used by this function
and we are dealing with anonymous memory, fall back to remapping the
location(s).

Signed-off-by: William Roche <william.roche@oracle.com>
Acked-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20250211212707.302391-3-william.roche@oracle.com
Signed-off-by: Peter Xu <peterx@redhat.com>
This commit is contained in:
William Roche 2025-02-11 21:27:06 +00:00 committed by Peter Xu
parent c1cda1c5f8
commit 30943e496f
1 changed files with 36 additions and 21 deletions
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57
system/physmem.c
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@ -2275,6 +2275,23 @@ void qemu_ram_free(RAMBlock *block)
} }
#ifndef _WIN32 #ifndef _WIN32
/* Simply remap the given VM memory location from start to start+length */
static int qemu_ram_remap_mmap(RAMBlock *block, uint64_t start, size_t length)
{
int flags, prot;
void *area;
void *host_startaddr = block->host + start;
assert(block->fd < 0);
flags = MAP_FIXED | MAP_ANONYMOUS;
flags |= block->flags & RAM_SHARED ? MAP_SHARED : MAP_PRIVATE;
flags |= block->flags & RAM_NORESERVE ? MAP_NORESERVE : 0;
prot = PROT_READ;
prot |= block->flags & RAM_READONLY ? 0 : PROT_WRITE;
area = mmap(host_startaddr, length, prot, flags, -1, 0);
return area != host_startaddr ? -errno : 0;
}
/* /*
* qemu_ram_remap - remap a single RAM page * qemu_ram_remap - remap a single RAM page
* *
@ -2292,9 +2309,7 @@ void qemu_ram_remap(ram_addr_t addr)
{ {
RAMBlock *block; RAMBlock *block;
uint64_t offset; uint64_t offset;
int flags; void *vaddr;
void *area, *vaddr;
int prot;
size_t page_size; size_t page_size;
RAMBLOCK_FOREACH(block) { RAMBLOCK_FOREACH(block) {
@ -2310,24 +2325,24 @@ void qemu_ram_remap(ram_addr_t addr)
} else if (xen_enabled()) { } else if (xen_enabled()) {
abort(); abort();
} else { } else {
flags = MAP_FIXED; if (ram_block_discard_range(block, offset, page_size) != 0) {
flags |= block->flags & RAM_SHARED ? /*
MAP_SHARED : MAP_PRIVATE; * Fall back to using mmap() only for anonymous mapping,
flags |= block->flags & RAM_NORESERVE ? MAP_NORESERVE : 0; * as if a backing file is associated we may not be able
prot = PROT_READ; * to recover the memory in all cases.
prot |= block->flags & RAM_READONLY ? 0 : PROT_WRITE; * So don't take the risk of using only mmap and fail now.
if (block->fd >= 0) { */
area = mmap(vaddr, page_size, prot, flags, block->fd, if (block->fd >= 0) {
offset + block->fd_offset); error_report("Could not remap RAM %s:%" PRIx64 "+%"
} else { PRIx64 " +%zx", block->idstr, offset,
flags |= MAP_ANONYMOUS; block->fd_offset, page_size);
area = mmap(vaddr, page_size, prot, flags, -1, 0); exit(1);
} }
if (area != vaddr) { if (qemu_ram_remap_mmap(block, offset, page_size) != 0) {
error_report("Could not remap RAM %s:%" PRIx64 "+%" PRIx64 error_report("Could not remap RAM %s:%" PRIx64 " +%zx",
" +%zx", block->idstr, offset, block->idstr, offset, page_size);
block->fd_offset, page_size); exit(1);
exit(1); }
} }
memory_try_enable_merging(vaddr, page_size); memory_try_enable_merging(vaddr, page_size);
qemu_ram_setup_dump(vaddr, page_size); qemu_ram_setup_dump(vaddr, page_size);