On Sun, Jul 7, 2013 at 2:59 PM, Gleb Natapov <gleb@xxxxxxxxxx> wrote:
> On Fri, Jul 05, 2013 at 11:13:17PM +0800, Arthur Chunqi Li wrote:
>> Fix read/write to IA32_FEATURE_CONTROL MSR in nested environment.
>>
>> This patch simulate this MSR in nested_vmx and the default value is
>> 0x0. BIOS should set it to 0x5 before VMXON. After setting the lock
>> bit, write to it will cause #GP(0).
>>
>> Signed-off-by: Arthur Chunqi Li <yzt356@xxxxxxxxx>
> The patch is heavily based on Nadav's one. You need to preserve
> authorship. Add From: and Nadav's Sign-off-by.
>
>> ---
>> arch/x86/kvm/vmx.c | 25 +++++++++++++++++++++----
>> arch/x86/kvm/x86.c | 3 ++-
>> 2 files changed, 23 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index 260a919..5e3d44e 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -373,6 +373,7 @@ struct nested_vmx {
>> * we must keep them pinned while L2 runs.
>> */
>> struct page *apic_access_page;
>> + u64 msr_ia32_feature_control;
>> };
>>
>> #define POSTED_INTR_ON 0
>> @@ -2277,8 +2278,11 @@ static int vmx_get_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
>>
>> switch (msr_index) {
>> case MSR_IA32_FEATURE_CONTROL:
>> - *pdata = 0;
>> - break;
>> + if (nested_vmx_allowed(vcpu)){
>> + *pdata = to_vmx(vcpu)->nested.msr_ia32_feature_control;
>> + break;
>> + }
>> + return 0;
>> case MSR_IA32_VMX_BASIC:
>> /*
>> * This MSR reports some information about VMX support. We
>> @@ -2356,9 +2360,13 @@ static int vmx_set_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
>> if (!nested_vmx_allowed(vcpu))
>> return 0;
>>
>> - if (msr_index == MSR_IA32_FEATURE_CONTROL)
>> - /* TODO: the right thing. */
>> + if (msr_index == MSR_IA32_FEATURE_CONTROL){
>> + if (to_vmx(vcpu)->nested.msr_ia32_feature_control
>> + & FEATURE_CONTROL_LOCKED)
>> + return 0;
>> + to_vmx(vcpu)->nested.msr_ia32_feature_control = data;
> You need to allow setting it from userspace, otherwise reset will not
> clear it.
As to my memory, if the lock bit of IA32_FEATURE_CONTROL is set, this
MSR cannot be set or reset. So what do you mean setting it from
userspace?
>
>> return 1;
>> + }
>> /*
>> * No need to treat VMX capability MSRs specially: If we don't handle
>> * them, handle_wrmsr will #GP(0), which is correct (they are readonly)
>> @@ -5595,6 +5603,15 @@ static int handle_vmon(struct kvm_vcpu *vcpu)
>> skip_emulated_instruction(vcpu);
>> return 1;
>> }
>> +
>> +#define VMXON_NEEDED_FEATURES \
> Avi asked to use const u64 here.
>
>> + (FEATURE_CONTROL_LOCKED | FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX)
>> + if ((vmx->nested.msr_ia32_feature_control & VMXON_NEEDED_FEATURES)
>> + != VMXON_NEEDED_FEATURES) {
>> + kvm_inject_gp(vcpu, 0);
>> + return 1;
>> + }
>> +
>> if (enable_shadow_vmcs) {
>> shadow_vmcs = alloc_vmcs();
>> if (!shadow_vmcs)
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index e8ba99c..2d4eb8e 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -850,7 +850,8 @@ static u32 msrs_to_save[] = {
>> #ifdef CONFIG_X86_64
>> MSR_CSTAR, MSR_KERNEL_GS_BASE, MSR_SYSCALL_MASK, MSR_LSTAR,
>> #endif
>> - MSR_IA32_TSC, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA
>> + MSR_IA32_TSC, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA,
>> + MSR_IA32_FEATURE_CONTROL
>> };
>>
>> static unsigned num_msrs_to_save;
>> --
>> 1.7.9.5
>
> --
> Gleb.
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