Re: [PATCH 16/28] KVM: VMX: Manually recalc all MSR intercepts on userspace MSR filter change

[Sean Christopherson]

On Fri, May 30, 2025, Xin Li wrote:
> > +
> > +	if (vcpu->arch.xfd_no_write_intercept)
> > +		vmx_disable_intercept_for_msr(vcpu, MSR_IA32_XFD, MSR_TYPE_RW);
> > +
> > +
> > +	vmx_set_intercept_for_msr(vcpu, MSR_IA32_SPEC_CTRL, MSR_TYPE_RW,
> > +				  !to_vmx(vcpu)->spec_ctrl);
> > +
> > +	if (kvm_cpu_cap_has(X86_FEATURE_XFD))
> > +		vmx_set_intercept_for_msr(vcpu, MSR_IA32_XFD_ERR, MSR_TYPE_R,
> > +					  !guest_cpu_cap_has(vcpu, X86_FEATURE_XFD));
> > +
> > +	if (boot_cpu_has(X86_FEATURE_IBPB))
> 
> I think Boris prefers using cpu_feature_enabled() instead — maybe this
> is a good opportunity to update this occurrence?

Yeah, I'm comfortable squeezing in that change.

> > +		vmx_set_intercept_for_msr(vcpu, MSR_IA32_PRED_CMD, MSR_TYPE_W,
> > +					  !guest_has_pred_cmd_msr(vcpu));
> > +
> > +	if (boot_cpu_has(X86_FEATURE_FLUSH_L1D))
> 
> Ditto.
> 
> > +		vmx_set_intercept_for_msr(vcpu, MSR_IA32_FLUSH_CMD, MSR_TYPE_W,
> > +					  !guest_cpu_cap_has(vcpu, X86_FEATURE_FLUSH_L1D));
> > +
> > +	/*
> > +	 * x2APIC and LBR MSR intercepts are modified on-demand and cannot be
> > +	 * filtered by userspace.
> > +	 */
> > +}