From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: [PATCH 07/13] KVM: SVM: Add intercept checks for descriptor table
 accesses
Date: Sat, 26 Mar 2011 11:43:47 +0200
Message-ID: <4D8DB553.7080508@redhat.com>
References: <1301045356-25257-1-git-send-email-joerg.roedel@amd.com> <1301045356-25257-8-git-send-email-joerg.roedel@amd.com>
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Cc: Marcelo Tosatti <mtosatti@redhat.com>, kvm@vger.kernel.org
To: Joerg Roedel <joerg.roedel@amd.com>
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On 03/25/2011 11:29 AM, Joerg Roedel wrote:
> This patch add intercept checks into the KVM instruction
> emulator to check for the 8 instructions that access the
> descriptor table addresses.
>
>
> +static struct opcode group6[] = {
> +	DI(ModRM,	 sldt),
> +	DI(ModRM,	 str),
> +	DI(ModRM | Priv, lldt),
> +	DI(ModRM | Priv, ltr),
> +	N, N, N, N,
> +};
> +
>   static struct group_dual group7 = { {
> -	N, N, DI(ModRM | SrcMem | Priv, lgdt), DI(ModRM | SrcMem | Priv, lidt),
> +	DI(ModRM | DstMem | Priv, sgdt), DI(ModRM | DstMem | Priv, sidt),
> +	DI(ModRM | SrcMem | Priv, lgdt), DI(ModRM | SrcMem | Priv, lidt),
>   	DI(SrcNone | ModRM | DstMem | Mov, smsw), N,
>   	DI(SrcMem16 | ModRM | Mov | Priv, lmsw),
>   	DI(SrcMem | ModRM | ByteOp | Priv | NoAccess, invlpg),

You're adding decode info for instructions that aren't emulated.  Safe 
AFAICT because of 'default: goto cannot_emulate', I guess.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.