On 7/23/25 19:04, Nikolai Barybin wrote:
QMP query-dump-guest-memory-capability reports win dump as available for
any x86 VM, which is false.
This patch implements proper query of vmcoreinfo and calculation of
guest note size. Based on that we can surely report whether win dump
available or not.
For further reference one may review this libvirt discussion:
https://lists.libvirt.org/archives/list/de...@lists.libvirt.org/thread/HJ3JRLWLGN3IKIC22OQ3PMZ4J3EFG5XB/#HJ3JRLWLGN3IKIC22OQ3PMZ4J3EFG5XB
[PATCH 0/4] Allow xml-configured coredump format on VM crash
Signed-off-by: Nikolai Barybin <nikolai.bary...@virtuozzo.com>
---
dump/win_dump.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 60 insertions(+)
diff --git a/dump/win_dump.c b/dump/win_dump.c
index 3162e8bd48..4bb1b28e63 100644
--- a/dump/win_dump.c
+++ b/dump/win_dump.c
@@ -14,14 +14,74 @@
#include "qemu/error-report.h"
#include "exec/cpu-defs.h"
#include "hw/core/cpu.h"
+#include "hw/misc/vmcoreinfo.h"
#include "qemu/win_dump_defs.h"
#include "win_dump.h"
#include "cpu.h"
+#include "elf.h"
#if defined(TARGET_X86_64)
+#define ELF_NOTE_SIZE(hdr_size, name_size, desc_size) \
+ ((DIV_ROUND_UP((hdr_size), 4) + \
+ DIV_ROUND_UP((name_size), 4) + \
+ DIV_ROUND_UP((desc_size), 4)) * 4)
+
bool win_dump_available(Error **errp)
{
+ uint64_t addr, note_head_size, name_size, desc_size;
+ uint32_t size;
+ uint16_t guest_format;
+ uint8_t *guest_note = NULL;
+ size_t guest_note_size = 0;
+ VMCoreInfoState *vmci = vmcoreinfo_find();
+ ArchDumpInfo dump_info = {};
+ GuestPhysBlockList blocks = {};
+ int ret;
+
+ if (!vmci || !vmci->has_vmcoreinfo)
+ return false;
+
+ ret = cpu_get_dump_info(&dump_info, &blocks);
This will not work IMHO. cpu_get_dump_info tries to operate
with a real guest memory, which is not provided. This means
that guest executable is impossible to find.
For me this is looking like Windows dump could not be enabled
after the patch.
+ if (ret < 0)
+ return false;
+
+ guest_format = le16_to_cpu(vmci->vmcoreinfo.guest_format);
+ if (guest_format != FW_CFG_VMCOREINFO_FORMAT_ELF)
+ return false;
+
+ size = le32_to_cpu(vmci->vmcoreinfo.size);
+ addr = le64_to_cpu(vmci->vmcoreinfo.paddr);
+ note_head_size = dump_info.d_class == ELFCLASS64 ?
+ sizeof(Elf64_Nhdr) : sizeof(Elf32_Nhdr);
note_head_size assignment could go to if below saving conditional
+
+ guest_note = g_malloc(size + 1);
leaked at the end of the call
+ cpu_physical_memory_read(addr, guest_note, size);
+ if (dump_info.d_class == ELFCLASS64) {
+ const Elf64_Nhdr *hdr = (void *)guest_note;
+ if (dump_info.d_endian == ELFDATA2LSB) {
+ name_size = cpu_to_le64(hdr->n_namesz);
+ desc_size = cpu_to_le64(hdr->n_descsz);
you are going to use these values as integers below,
thus it is required to do conversion from the guest
endianity to the local one, i.e. le64_to_cpu
+ } else {
+ name_size = cpu_to_be64(hdr->n_namesz);
+ desc_size = cpu_to_be64(hdr->n_descsz);
same as above
+ }
+ } else {
+ const Elf32_Nhdr *hdr = (void *)guest_note;
+ if (dump_info.d_endian == ELFDATA2LSB) {
+ name_size = cpu_to_le32(hdr->n_namesz);
+ desc_size = cpu_to_le32(hdr->n_descsz);
same as above
+ } else {
+ name_size = cpu_to_be32(hdr->n_namesz);
+ desc_size = cpu_to_be32(hdr->n_descsz);
same as above
+ }
+ }
+
+ guest_note_size = ELF_NOTE_SIZE(note_head_size, name_size, desc_size);
+ if (guest_note_size != VMCOREINFO_WIN_DUMP_NOTE_SIZE64 &&
+ guest_note_size != VMCOREINFO_WIN_DUMP_NOTE_SIZE32)
+ return false;
+
personally I prefer
return guest_note_size == VMCOREINFO_WIN_DUMP_NOTE_SIZE64 ||
guest_note_size == VMCOREINFO_WIN_DUMP_NOTE_SIZE32;
return true;
}
