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

Paolo Bonzini
2014-08-19T09:11:13Z

Il 19/08/2014 11:04, Wanpeng Li ha scritto:
> 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;
> }
>
>

Thanks, these two patches look good. Please write a testcase for
kvm-unit-tests (x86/msr.c), too.

Paolo