Re: [Qemu-devel] [PATCH] cpu: flush TB cache when loading VMState

[Richard Henderson]

On 01/10/2018 05:48 AM, Pavel Dovgalyuk wrote:
> Flushing TB cache is required because TBs key in the cache may match
> different code which existed in the previous state.
> 
> Signed-off-by: Pavel Dovgalyuk <address@hidden>
> Signed-off-by: Maria Klimushenkova <address@hidden>
> ---
>  exec.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/exec.c b/exec.c
> index 4722e52..ff31e71 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -622,6 +622,7 @@ static int cpu_common_post_load(void *opaque, int 
> version_id)
>         version_id is increased. */
>      cpu->interrupt_request &= ~0x01;
>      tlb_flush(cpu);
> +    tb_flush(cpu);

I'm not necessarily objecting, but what do you mean by "may match different 
code"?

What this patch suggests is that the inputs to the computation of TB->FLAGS are
different for some unspecified reason.  Without further explanation, to me this
suggests a bug in vmstate save/restore.

What is the observed problem here?


r~