linux-kernel - Re: [PATCH 5/5] KVM: x86: #GP when attempts to write reserved bits of Variable Range MTRRs

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Date:	Mon, 18 Aug 2014 20:27:29 +0800
From:	Wanpeng Li <wanpeng.li@...ux.intel.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	Gleb Natapov <gleb@...nel.org>, hpa@...or.com, x86@...nel.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] KVM: x86: #GP when attempts to write reserved bits
 of Variable Range MTRRs

Hi Paolo,
On Mon, Aug 18, 2014 at 05:50:31PM +0800, Wanpeng Li wrote:
>Section 11.11.2.3 of the SDM mentions "All other bits in the IA32_MTRR_PHYSBASEn 
>and IA32_MTRR_PHYSMASKn registers are reserved; the processor generates a 
>general-protection exception(#GP) if software attempts to write to them". This 
>patch do it in kvm.
>

How about this one?

Regards,
Wanpeng Li 

>Signed-off-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
>---
> arch/x86/kvm/x86.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
>diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>index caaffeb..aa64c70 100644
>--- a/arch/x86/kvm/x86.c
>+++ b/arch/x86/kvm/x86.c
>@@ -1769,11 +1769,22 @@ static bool mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data)
> 	/* variable MTRRs */
> 	if (msr >= 0x200 && msr < 0x200 + 2 * KVM_NR_VAR_MTRR) {
> 		int idx, is_mtrr_mask;
>+		u64 mask = 0;
> 
> 		idx = (msr - 0x200) / 2;
> 		is_mtrr_mask = msr - 0x200 - 2 * idx;
>-		if (!is_mtrr_mask)
>-			return valid_mtrr_type(data & 0xff);
>+		for (i = 63; i > boot_cpu_data.x86_phys_bits; i--)
>+			mask |= (1ULL << i);
>+		if (!is_mtrr_mask) {
>+			if (!valid_mtrr_type(data & 0xff))
>+				return false;
>+			mask |= 0xf00;
>+		} else
>+			mask |= 0x7ff;
>+		if (data & mask) {
>+			kvm_inject_gp(vcpu, 0);
>+			return false;
>+		}
> 	}
> 	return true;
> }
>-- 
>1.9.1
--
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