linux-kernel - Re: [PATCH] KVM: emulator: Use linearize() when fetching instructions.

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Message-ID: <4DAADC72.5040503@redhat.com>
Date:	Sun, 17 Apr 2011 15:26:26 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Nelson Elhage <nelhage@...lice.com>
CC:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: emulator: Use linearize() when fetching instructions.

On 04/15/2011 06:27 AM, Nelson Elhage wrote:
> This means that the truncation behavior in linearize needs to grow an additional
> slight piece of complexity: when fetching, truncation is dependent on the
> execution mode, instead of the current address size.
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index a5f63d4..d3d43a7 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -542,7 +542,7 @@ static int emulate_nm(struct x86_emulate_ctxt *ctxt)
>
>   static int linearize(struct x86_emulate_ctxt *ctxt,
>   		     struct segmented_address addr,
> -		     unsigned size, bool write,
> +		     unsigned size, bool write, bool fetch,

Calls to functions with strings of bool arguments are confusing.  Please 
make this __linearize, and introduce a new linearize() which doesn't 
have a fetch argument.

>   		ulong *linear)
>   {
>   	struct decode_cache *c =&ctxt->decode;
> @@ -602,7 +602,7 @@ static int linearize(struct x86_emulate_ctxt *ctxt,
>   		}
>   		break;
>   	}

linearize() will currently fault on an unreadable code segment.  Need to 
avoid that on instruction fetches.

> -	if (c->ad_bytes != 8)
> +	if (fetch ? ctxt->mode != X86EMUL_MODE_PROT64 : c->ad_bytes != 8)
>   		la&= (u32)-1;
>   	*linear = la;
>   	return X86EMUL_CONTINUE;

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

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