On 07.11.24 11:21, “William Roche wrote:
From: William Roche <william.roche@xxxxxxxxxx>
We take into account the recorded page sizes to repair the
memory locations, calling ram_block_discard_range() to punch a hole
in the backend file when necessary and regenerate a usable memory.
Fall back to unmap/remap the memory location(s) if the kernel doesn't
support the madvise calls used by ram_block_discard_range().
Hugetlbfs poison case is also taken into account as a hole punch
with fallocate will reload a new page when first touched.
Signed-off-by: William Roche <william.roche@xxxxxxxxxx>
---
system/physmem.c | 50 +++++++++++++++++++++++++++++-------------------
1 file changed, 30 insertions(+), 20 deletions(-)
diff --git a/system/physmem.c b/system/physmem.c
index 750604d47d..dfea120cc5 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -2197,27 +2197,37 @@ void qemu_ram_remap(ram_addr_t addr, ram_addr_t length)
} else if (xen_enabled()) {
abort();
} else {
- flags = MAP_FIXED;
- 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;
- if (block->fd >= 0) {
- area = mmap(vaddr, length, prot, flags, block->fd,
- offset + block->fd_offset);
- } else {
- flags |= MAP_ANONYMOUS;
- area = mmap(vaddr, length, prot, flags, -1, 0);
- }
- if (area != vaddr) {
- error_report("Could not remap addr: "
- RAM_ADDR_FMT "@" RAM_ADDR_FMT "",
- length, addr);
- exit(1);
+ if (ram_block_discard_range(block, offset + block->fd_offset,
+ length) != 0) {
+ if (length > TARGET_PAGE_SIZE) {
+ /* punch hole is mandatory on hugetlbfs */
+ error_report("large page recovery failure addr: "
+ RAM_ADDR_FMT "@" RAM_ADDR_FMT "",
+ length, addr);
+ exit(1);
+ }
For shared memory we really need it.
Private file-backed is weird ... because we don't know if the shared or
the private page is problematic ... :(
Maybe we should just do:
if (block->fd >= 0) {
/* mmap(MAP_FIXED) cannot reliably zap our problematic page. */
error_report(...);
exit(-1);
}
Or alternatively
if (block->fd >= 0 && qemu_ram_is_shared(block)) {
/* mmap() cannot possibly zap our problematic page. */
error_report(...);
exit(-1);
} else if (block->fd >= 0) {
/*
* MAP_PRIVATE file-backed ... mmap() can only zap the private
* page, not the shared one ... we don't know which one is
* problematic.
*/
warn_report(...);
}
+ flags = MAP_FIXED;
+ 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;
+ if (block->fd >= 0) {
+ area = mmap(vaddr, length, prot, flags, block->fd,
+ offset + block->fd_offset);
+ } else {
+ flags |= MAP_ANONYMOUS;
+ area = mmap(vaddr, length, prot, flags, -1, 0);
+ }
+ if (area != vaddr) {
+ error_report("Could not remap addr: "
+ RAM_ADDR_FMT "@" RAM_ADDR_FMT "",
+ length, addr);
+ exit(1);
+ }
+ memory_try_enable_merging(vaddr, length);
+ qemu_ram_setup_dump(vaddr, length);
Can we factor the mmap hack out into a separate helper function to clean
this up a bit?
--
Cheers,
David / dhildenb
