Re: [PATCH v2 2/3] dump: add crash_occurred flag to QEMUCPUState

On 2026/08/05 18:05, Zhengrong Li wrote:
> Add is_crash_occurred_cpu field to QEMUCPUState so that
> dump-guest-memory can record which CPU triggered the guest
> panic.
> 
> The new field is appended after kernel_gs_base, so existing
> tools that check the 'size' field can safely ignore it when
> reading older dumps.
> 
> Changes since v1:
>    - Revert QEMUCPUSTATE_VERSION bump (not needed, tools check size)
>    - Move crash_occurred check outside #ifdef TARGET_X86_64 to fix
>      -Werror=unused-variable on i386 builds (reported by Akihiko Odaki)
>    - Use linux.alibaba.com identity
> 
> Signed-off-by: Zhengrong Li <[email protected]>
> ---
>   contrib/elf2dmp/qemu_elf.h | 2 ++
>   target/i386/arch_dump.c    | 6 ++++++
>   2 files changed, 8 insertions(+)
> 
> diff --git a/contrib/elf2dmp/qemu_elf.h b/contrib/elf2dmp/qemu_elf.h
> index adc50238b4..3b28332e67 100644
> --- a/contrib/elf2dmp/qemu_elf.h
> +++ b/contrib/elf2dmp/qemu_elf.h
> @@ -27,6 +27,8 @@ typedef struct QEMUCPUState {
>       QEMUCPUSegment ldt, tr, gdt, idt;
>       uint64_t cr[5];
>       uint64_t kernel_gs_base;
> +    uint8_t  is_crash_occurred_cpu;
> +    uint8_t  pad[7];

Growing QEMUCPUState from 440 to 448 bytes confuses init_states() in 
contrib/elf2dmp/qemu_elf.c and makes valid version-1 notes appear to 
lack kernel_gs_base, despite that field occupying bytes 432–439.

Patch 3 fixes homogeneous old dumps, but that field-specific size 
detection belongs in this patch for bisectability and to support its 
compatibility claim. Please see docs/devel/submitting-a-patch.rst for 
the bisect requirement.

Regards,
Akihiko Odaki

>   } QEMUCPUState;
>   
>   int is_system(QEMUCPUState *s);
> diff --git a/target/i386/arch_dump.c b/target/i386/arch_dump.c
> index 16e47c4747..8ce2c7e9bb 100644
> --- a/target/i386/arch_dump.c
> +++ b/target/i386/arch_dump.c
> @@ -264,6 +264,8 @@ struct QEMUCPUState {
>        * by checking 'size' field.
>        */
>       uint64_t kernel_gs_base;
> +    uint8_t  is_crash_occurred_cpu;
> +    uint8_t  pad[7];
>   };
>   
>   typedef struct QEMUCPUState QEMUCPUState;
> @@ -279,6 +281,7 @@ static void copy_segment(QEMUCPUSegment *d, SegmentCache *s)
>   
>   static void qemu_get_cpustate(QEMUCPUState *s, CPUX86State *env)
>   {
> +    CPUState *cs = env_cpu(env);
>       memset(s, 0, sizeof(QEMUCPUState));
>   
>       s->version = QEMUCPUSTATE_VERSION;
> @@ -325,6 +328,9 @@ static void qemu_get_cpustate(QEMUCPUState *s, CPUX86State *env)
>   #ifdef TARGET_X86_64
>       s->kernel_gs_base = env->kernelgsbase;
>   #endif
> +    if (cs->crash_occurred) {
> +        s->is_crash_occurred_cpu = 1;
> +    }
>   }
>   
>   static inline int cpu_write_qemu_note(WriteCoreDumpFunction f,