On 6/11/2025 6:57 AM, Sean Christopherson wrote:
> Refactor {svm,vmx}_disable_intercept_for_msr() to simplify the handling of
> userspace filters that disallow access to an MSR. The more complicated
> logic is no longer needed or justified now that KVM recalculates all MSR
> intercepts on a userspace MSR filter change, i.e. now that KVM doesn't
> need to also update shadow bitmaps.
>
> No functional change intended.
>
> Suggested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/x86/kvm/svm/svm.c | 24 ++++++++++--------------
> arch/x86/kvm/vmx/vmx.c | 24 ++++++++++--------------
> 2 files changed, 20 insertions(+), 28 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index e3c49c763225..5453478d1ca3 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -691,24 +691,20 @@ void svm_disable_intercept_for_msr(struct kvm_vcpu *vcpu, u32 msr, int type)
> void *msrpm = svm->msrpm;
>
> /* Don't disable interception for MSRs userspace wants to handle. */
> - if ((type & MSR_TYPE_R) &&
> - !kvm_msr_allowed(vcpu, msr, KVM_MSR_FILTER_READ)) {
> - svm_set_msr_bitmap_read(msrpm, msr);
> - type &= ~MSR_TYPE_R;
> + if (type & MSR_TYPE_R) {
> + if (kvm_msr_allowed(vcpu, msr, KVM_MSR_FILTER_READ))
> + svm_clear_msr_bitmap_read(msrpm, msr);
> + else
> + svm_set_msr_bitmap_read(msrpm, msr);
> }
>
> - if ((type & MSR_TYPE_W) &&
> - !kvm_msr_allowed(vcpu, msr, KVM_MSR_FILTER_WRITE)) {
> - svm_set_msr_bitmap_write(msrpm, msr);
> - type &= ~MSR_TYPE_W;
> + if (type & MSR_TYPE_W) {
> + if (kvm_msr_allowed(vcpu, msr, KVM_MSR_FILTER_WRITE))
> + svm_clear_msr_bitmap_write(msrpm, msr);
> + else
> + svm_set_msr_bitmap_write(msrpm, msr);
> }
>
> - if (type & MSR_TYPE_R)
> - svm_clear_msr_bitmap_read(msrpm, msr);
> -
> - if (type & MSR_TYPE_W)
> - svm_clear_msr_bitmap_write(msrpm, msr);
> -
> svm_hv_vmcb_dirty_nested_enlightenments(vcpu);
> svm->nested.force_msr_bitmap_recalc = true;
> }
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index bdff81f8288d..277c6b5b5d5f 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -3962,23 +3962,19 @@ void vmx_disable_intercept_for_msr(struct kvm_vcpu *vcpu, u32 msr, int type)
>
> vmx_msr_bitmap_l01_changed(vmx);
>
> - if ((type & MSR_TYPE_R) &&
> - !kvm_msr_allowed(vcpu, msr, KVM_MSR_FILTER_READ)) {
> - vmx_set_msr_bitmap_read(msr_bitmap, msr);
> - type &= ~MSR_TYPE_R;
> + if (type & MSR_TYPE_R) {
> + if (kvm_msr_allowed(vcpu, msr, KVM_MSR_FILTER_READ))
> + vmx_clear_msr_bitmap_read(msr_bitmap, msr);
> + else
> + vmx_set_msr_bitmap_read(msr_bitmap, msr);
> }
>
> - if ((type & MSR_TYPE_W) &&
> - !kvm_msr_allowed(vcpu, msr, KVM_MSR_FILTER_WRITE)) {
> - vmx_set_msr_bitmap_write(msr_bitmap, msr);
> - type &= ~MSR_TYPE_W;
> + if (type & MSR_TYPE_W) {
> + if (kvm_msr_allowed(vcpu, msr, KVM_MSR_FILTER_WRITE))
> + vmx_clear_msr_bitmap_write(msr_bitmap, msr);
> + else
> + vmx_set_msr_bitmap_write(msr_bitmap, msr);
> }
> -
> - if (type & MSR_TYPE_R)
> - vmx_clear_msr_bitmap_read(msr_bitmap, msr);
> -
> - if (type & MSR_TYPE_W)
> - vmx_clear_msr_bitmap_write(msr_bitmap, msr);
> }
>
> void vmx_enable_intercept_for_msr(struct kvm_vcpu *vcpu, u32 msr, int type)
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>