linux-kernel - Re: [PATCH 2/2] deal with interrupt shadow state for emulated instruction

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Message-ID: <4A06D21C.2060008@redhat.com>
Date:	Sun, 10 May 2009 16:09:48 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Glauber Costa <glommer@...hat.com>
CC:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	"H. Peter Anvin" <hpa@...or.com>, Gleb Natapov <gleb@...hat.com>
Subject: Re: [PATCH 2/2] deal with interrupt shadow state for emulated instruction

Glauber Costa wrote:
> we currently unblock shadow interrupt state when we skip an instruction,
> but failing to do so when we actually emulate one. This blocks interrupts
> in key instruction blocks, in particular sti; hlt; sequences
>
> If the instruction emulated is an sti, we have to block shadow interrupts.
> The same goes for mov ss. pop ss also needs it, but we don't currently
> emulate it.
>
> Without this patch, I cannot boot gpxe option roms at vmx machines.
> This is described at https://bugzilla.redhat.com/show_bug.cgi?id=494469
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 3d8fcc5..c456aa5 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2362,7 +2362,7 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
>  			u16 error_code,
>  			int emulation_type)
>  {
> -	int r;
> +	int r, shadow_mask;
>  	struct decode_cache *c;
>  
>  	kvm_clear_exception_queue(vcpu);
> @@ -2415,7 +2415,12 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
>  		return EMULATE_DONE;
>  	}
>  
> +	vcpu->arch.emulate_ctxt.interruptibility = 0;
>   

If the instruction is sti or mov ss, this is ouput only.  Otherwise, it 
is an input/output parameter.

To reduce confusion suggest moving this statement to x86_emulate_insn, 
so it can be an output-only parameter.


-- 
error compiling committee.c: too many arguments to function

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