On 10.01.25 22:14, “William Roche wrote:
From: William Roche <william.roche@xxxxxxxxxx>
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@xxxxxxxxxx>
---
system/physmem.c | 57 ++++++++++++++++++++++++++++++------------------
1 file changed, 36 insertions(+), 21 deletions(-)
diff --git a/system/physmem.c b/system/physmem.c
index 7a87548f99..ae1caa97d8 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -2180,13 +2180,32 @@ void qemu_ram_free(RAMBlock *block)
}
#ifndef _WIN32
+/* Simply remap the given VM memory location from start to start+length */
+static void 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);
+ if (area != host_startaddr) {
+ error_report("Could not remap addr: " RAM_ADDR_FMT "@" RAM_ADDR_FMT "",
+ length, start);
+ exit(1);
+ }
Can we return an error and have a single error printed in the caller?
return area != host_startaddr ? -errno : 0;
+}
+
void qemu_ram_remap(ram_addr_t addr)
{
RAMBlock *block;
ram_addr_t offset;
- int flags;
- void *area, *vaddr;
- int prot;
+ void *vaddr;
size_t page_size;
RAMBLOCK_FOREACH(block) {
@@ -2202,24 +2221,20 @@ void qemu_ram_remap(ram_addr_t addr)
} 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, page_size, prot, flags, block->fd,
- offset + block->fd_offset);
- } else {
- flags |= MAP_ANONYMOUS;
- area = mmap(vaddr, page_size, prot, flags, -1, 0);
- }
- if (area != vaddr) {
- error_report("Could not remap addr: "
- RAM_ADDR_FMT "@" RAM_ADDR_FMT "",
- page_size, addr);
- exit(1);
+ if (ram_block_discard_range(block, offset, page_size) != 0) {
+ /*
+ * Fall back to using mmap() only for anonymous mapping,
+ * as if a backing file is associated we may not be able
+ * to recover the memory in all cases.
+ * So don't take the risk of using only mmap and fail now.
+ */
+ if (block->fd >= 0) {
+ error_report("Memory poison recovery failure addr: "
+ RAM_ADDR_FMT "@" RAM_ADDR_FMT "",
+ page_size, addr);
See my error message proposal as reply to v4 patch #1: we should similarly
just print rb->idstr, offset and page_size like ram_block_discard_range() does.
ram_addr_t is weird and not helpful for users.
To have a single error
if (ram_block_discard_range(block, offset, page_size) != 0) {
/* ...
if (block->fd >= 0 || qemu_ram_remap_mmap(block, offset, page_size)) {
error_report() ... // use proposal from my reply to v4 patch #1
exit(1);
}
}
--
Cheers,
David / dhildenb
