Re: [PATCH 2/4] KVM: VMX: Setup MSR bitmap only when has msr_bitmap capability

[Xiaoyao Li <xiaoyao.li@xxxxxxxxx>]

On 10/16/2019 8:40 AM, Krish Sadhukhan wrote:
> On 10/15/2019 09:40 AM, Xiaoyao Li wrote:
> > Move the MSR bitmap setup codes to vmx_vmcs_setup() and only setup them
> > when hardware has msr_bitmap capability.
> >
> > Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
> > ---
> >   arch/x86/kvm/vmx/vmx.c | 39 ++++++++++++++++++++-------------------
> >   1 file changed, 20 insertions(+), 19 deletions(-)
> >
> > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> > index 58b77a882426..7051511c27c2 100644
> > --- a/arch/x86/kvm/vmx/vmx.c
> > +++ b/arch/x86/kvm/vmx/vmx.c
> > @@ -4164,12 +4164,30 @@ static void ept_set_mmio_spte_mask(void)
> >   static void vmx_vmcs_setup(struct vcpu_vmx *vmx)
> >   {
> >       int i;
> > +    unsigned long *msr_bitmap;
> >       if (nested)
> >           nested_vmx_vmcs_setup();
> > -    if (cpu_has_vmx_msr_bitmap())
> > -        vmcs_write64(MSR_BITMAP, __pa(vmx->vmcs01.msr_bitmap));
> > +    if (cpu_has_vmx_msr_bitmap()) {
> > +        msr_bitmap = vmx->vmcs01.msr_bitmap;
> > +        vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_TSC, 
> > MSR_TYPE_R);
>
> vmx_disable_intercept_for_msr() also calls cpu_has_vmx_msr_bitmap(), 
> which means we are repeating the check. A cleaner approach is to remove 
> the call to cpu_has_vmx_msr_bitmap()  from 
> vmx_disable_intercept_for_msr()  and let its callers do the check just 
> like you are doing here.

Right.
I'll improve it. Thanks!

> > +        vmx_disable_intercept_for_msr(msr_bitmap, MSR_FS_BASE, 
> > MSR_TYPE_RW);
> > +        vmx_disable_intercept_for_msr(msr_bitmap, MSR_GS_BASE, 
> > MSR_TYPE_RW);
> > +        vmx_disable_intercept_for_msr(msr_bitmap, MSR_KERNEL_GS_BASE, 
> > MSR_TYPE_RW);
> > +        vmx_disable_intercept_for_msr(msr_bitmap, 
> > MSR_IA32_SYSENTER_CS, MSR_TYPE_RW);
> > +        vmx_disable_intercept_for_msr(msr_bitmap, 
> > MSR_IA32_SYSENTER_ESP, MSR_TYPE_RW);
> > +        vmx_disable_intercept_for_msr(msr_bitmap, 
> > MSR_IA32_SYSENTER_EIP, MSR_TYPE_RW);
> > +        if (kvm_cstate_in_guest(vmx->vcpu.kvm)) {
> > +            vmx_disable_intercept_for_msr(msr_bitmap, 
> > MSR_CORE_C1_RES, MSR_TYPE_R);
> > +            vmx_disable_intercept_for_msr(msr_bitmap, 
> > MSR_CORE_C3_RESIDENCY, MSR_TYPE_R);
> > +            vmx_disable_intercept_for_msr(msr_bitmap, 
> > MSR_CORE_C6_RESIDENCY, MSR_TYPE_R);
> > +            vmx_disable_intercept_for_msr(msr_bitmap, 
> > MSR_CORE_C7_RESIDENCY, MSR_TYPE_R);
> > +        }
> > +
> > +        vmcs_write64(MSR_BITMAP, __pa(msr_bitmap));
> > +    }
> > +    vmx->msr_bitmap_mode = 0;
> >       vmcs_write64(VMCS_LINK_POINTER, -1ull); /* 22.3.1.5 */
> > @@ -6697,7 +6715,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct 
> > kvm *kvm, unsigned int id)
> >   {
> >       int err;
> >       struct vcpu_vmx *vmx;
> > -    unsigned long *msr_bitmap;
> >       int cpu;
> >       BUILD_BUG_ON_MSG(offsetof(struct vcpu_vmx, vcpu) != 0,
> > @@ -6754,22 +6771,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct 
> > kvm *kvm, unsigned int id)
> >       if (err < 0)
> >           goto free_msrs;
> > -    msr_bitmap = vmx->vmcs01.msr_bitmap;
> > -    vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_TSC, MSR_TYPE_R);
> > -    vmx_disable_intercept_for_msr(msr_bitmap, MSR_FS_BASE, MSR_TYPE_RW);
> > -    vmx_disable_intercept_for_msr(msr_bitmap, MSR_GS_BASE, MSR_TYPE_RW);
> > -    vmx_disable_intercept_for_msr(msr_bitmap, MSR_KERNEL_GS_BASE, 
> > MSR_TYPE_RW);
> > -    vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_SYSENTER_CS, 
> > MSR_TYPE_RW);
> > -    vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_SYSENTER_ESP, 
> > MSR_TYPE_RW);
> > -    vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_SYSENTER_EIP, 
> > MSR_TYPE_RW);
> > -    if (kvm_cstate_in_guest(kvm)) {
> > -        vmx_disable_intercept_for_msr(msr_bitmap, MSR_CORE_C1_RES, 
> > MSR_TYPE_R);
> > -        vmx_disable_intercept_for_msr(msr_bitmap, 
> > MSR_CORE_C3_RESIDENCY, MSR_TYPE_R);
> > -        vmx_disable_intercept_for_msr(msr_bitmap, 
> > MSR_CORE_C6_RESIDENCY, MSR_TYPE_R);
> > -        vmx_disable_intercept_for_msr(msr_bitmap, 
> > MSR_CORE_C7_RESIDENCY, MSR_TYPE_R);
> > -    }
> > -    vmx->msr_bitmap_mode = 0;
> > -
> >       vmx->loaded_vmcs = &vmx->vmcs01;
> >       cpu = get_cpu();
> >       vmx_vcpu_load(&vmx->vcpu, cpu);