Re: [Qemu-devel] [PATCH v3] KVM: nVMX: Fix read/write to MSR_IA32_FEATURE_CONTROL

[Gleb Natapov]

On Sun, Jul 07, 2013 at 11:07:33PM +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).
> 
> Another QEMU patch is also needed to handle emulation of reset
> and migration. Reset to vCPU should clear this MSR and migration
> should reserve value of it.
> 
> This patch is based on Nadav's previous commit.
> http://permalink.gmane.org/gmane.comp.emulators.kvm.devel/88478
> 
> Signed-off-by: Nadav Har'El <nyh <at> il.ibm.com>

Nadav's address is address@hidden Also the first line of the
email should be From: Nadav Har'El <address@hidden>

> Signed-off-by: Arthur Chunqi Li <address@hidden>
> ---
>  arch/x86/kvm/vmx.c |   32 ++++++++++++++++++++++++++------
>  arch/x86/kvm/x86.c |    3 ++-
>  2 files changed, 28 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index a7e1855..a64efd0 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
> @@ -2282,8 +2283,11 @@ 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)){
Space after { here and everywhere. Use scripts/checkpatch.pl to check
your patches for style issues.

> +                     *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
> @@ -2356,14 +2360,21 @@ static int vmx_get_vmx_msr(struct kvm_vcpu *vcpu, u32 
> msr_index, u64 *pdata)
>       return 1;
>  }
>  
> -static int vmx_set_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
> +static int vmx_set_vmx_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  {
> +     u32 msr_index = msr_info->index;
> +     u64 data = msr_info->data;
> +     bool host_initialized = msr_info->host_initiated;
Leave empty line here.

>       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 (!host_initialized && 
> to_vmx(vcpu)->nested.msr_ia32_feature_control
> +                             & FEATURE_CONTROL_LOCKED)
> +                     return 0;
> +             to_vmx(vcpu)->nested.msr_ia32_feature_control = data;
>               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)
> @@ -2494,7 +2505,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct 
> msr_data *msr_info)
>                       return 1;
>               /* Otherwise falls through */
>       default:
> -             if (vmx_set_vmx_msr(vcpu, msr_index, data))
> +             if (vmx_set_vmx_msr(vcpu, msr_info))
>                       break;
>               msr = find_msr_entry(vmx, msr_index);
>               if (msr) {
> @@ -5576,6 +5587,8 @@ static int handle_vmon(struct kvm_vcpu *vcpu)
>       struct kvm_segment cs;
>       struct vcpu_vmx *vmx = to_vmx(vcpu);
>       struct vmcs *shadow_vmcs;
> +     const u64 VMXON_NEEDED_FEATURES = FEATURE_CONTROL_LOCKED
> +             | FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX;
>  
>       /* The Intel VMX Instruction Reference lists a bunch of bits that
>        * are prerequisite to running VMXON, most notably cr4.VMXE must be
> @@ -5604,6 +5617,13 @@ static int handle_vmon(struct kvm_vcpu *vcpu)
>               skip_emulated_instruction(vcpu);
>               return 1;
>       }
> +
> +     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 d21bce5..cff77c4 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.