Re: [PATCH]: KVM: Fix cmpxchg for writeback changes

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Aurelien Jarno wrote:
>   KVM: Fix writeback for cmpxchg instruction
>
>   The writeback fixes (02c03a326a5df825cc01de426f72e160db2b9538) broke
>   cmpxchg emulation.  The patch below fixes that.
>
>   Signed-off-by: Aurelien Jarno <aurelien-rXXEIb44qovR7s880joybQ@public.gmane.org>
>
> diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
> index 21ce977..9d30d10 100644
> --- a/drivers/kvm/x86_emulate.c
> +++ b/drivers/kvm/x86_emulate.c
> @@ -1275,7 +1275,7 @@ twobyte_insn:
>  		src.val = _regs[VCPU_REGS_RAX];
>  		emulate_2op_SrcV("cmp", src, dst, _eflags);
>  		/* Always write back. The question is: where to? */
> -		d |= Mov;
> +		no_wb = 0;
>  		if (_eflags & EFLG_ZF) {
>  			/* Success: write back to memory. */
>  			dst.val = src.orig_val;
>
>   

But no_wb defaults to zero?


-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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