linux-kernel - [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 17:50:31 +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,
	Wanpeng Li <wanpeng.li@...ux.intel.com>
Subject: [PATCH 5/5] KVM: x86: #GP when attempts to write reserved bits of Variable Range MTRRs 

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.

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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