[PATCH v2 3/3] KVM: x86: #GP when attempts to write reserved bits of Variable Range MTRRs

Wanpeng Li
2014-08-19T09:02:39Z

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@linux.intel.com>
---
arch/x86/kvm/x86.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fb3ea7a..b85da5f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1726,6 +1726,7 @@ static bool valid_mtrr_type(unsigned t)
static bool mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data)
{
int i;
+ u64 mask = 0;

if (!msr_mtrr_valid(msr))
return false;
@@ -1749,10 +1750,21 @@ static bool mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data)
/* variable MTRRs */
WARN_ON(!(msr >= 0x200 && msr < 0x200 + 2 * KVM_NR_VAR_MTRR));

- if ((msr & 1) == 0)
+ for (i = 63; i > boot_cpu_data.x86_phys_bits; i--)
+ mask |= (1ULL << i);
+ if ((msr & 1) == 0) {
/* MTRR base */
- return valid_mtrr_type(data & 0xff);
- /* MTRR mask */
+ if (!valid_mtrr_type(data & 0xff))
+ return false;
+ mask |= 0xf00;
+ } else
+ /* MTRR mask */
+ mask |= 0x7ff;
+ if (data & mask) {
+ kvm_inject_gp(vcpu, 0);
+ return false;
+ }
+
return true;
}

--
1.9.1