Messages in this thread Patch in this message | | | Date | Mon, 8 Nov 2021 17:44:43 +0000 | From | Sean Christopherson <> | Subject | Re: [PATCH v5 3/7] KVM: X86: Expose IA32_PKRS MSR |
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On Wed, Aug 11, 2021, Chenyi Qiang wrote: > + u32 pkrs;
...
> @@ -1115,6 +1117,7 @@ void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu) > #endif > unsigned long fs_base, gs_base; > u16 fs_sel, gs_sel; > + u32 host_pkrs;
As mentioned in the previosu patch, I think it makes sense to track this as a u64 so that the only place in KVM that deas with the u64<=>u32 conversion is the below
host_pkrs = get_current_pkrs();
> int i; > > vmx->req_immediate_exit = false; > @@ -1150,6 +1153,20 @@ void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu) > */ > host_state->ldt_sel = kvm_read_ldt(); > > + /* > + * Update the host pkrs vmcs field before vcpu runs. > + * The setting of VM_EXIT_LOAD_IA32_PKRS can ensure > + * kvm_cpu_cap_has(X86_FEATURE_PKS) && > + * guest_cpuid_has(vcpu, X86_FEATURE_PKS) > + */ > + if (vm_exit_controls_get(vmx) & VM_EXIT_LOAD_IA32_PKRS) { > + host_pkrs = get_current_pkrs(); > + if (unlikely(host_pkrs != host_state->pkrs)) { > + vmcs_write64(HOST_IA32_PKRS, host_pkrs); > + host_state->pkrs = host_pkrs; > + } > + } > + > #ifdef CONFIG_X86_64 > savesegment(ds, host_state->ds_sel); > savesegment(es, host_state->es_sel); > @@ -1371,6 +1388,15 @@ void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags) > vmx->emulation_required = emulation_required(vcpu); > } > > +static void vmx_set_pkrs(struct kvm_vcpu *vcpu, u64 pkrs) > +{
Hrm. Ideally this would be open coded in vmx_set_msr(). Long term, the RESET/INIT paths should really treat MSR updates as "normal" host_initiated writes instead of having to manually handle every MSR.
That would be a bit gross to handle in vmx_vcpu_reset() since it would have to create a struct msr_data (because __kvm_set_msr() isn't exposed to vendor code), but since vcpu->arch.pkrs is relevant to the MMU I think it makes sense to initiate the write from common x86.
E.g. this way there's not out-of-band special code, vmx_vcpu_reset() is kept clean, and if/when SVM gains support for PKRS this particular path Just Works. And it would be an easy conversion for my pipe dream plan of handling MSRs at RESET/INIT via a list of MSRs+values.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index ac83d873d65b..55881d13620f 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -11147,6 +11147,9 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) kvm_set_rflags(vcpu, X86_EFLAGS_FIXED); kvm_rip_write(vcpu, 0xfff0);
+ if (kvm_cpu_cap_has(X86_FEATURE_PKS)) + __kvm_set_msr(vcpu, MSR_IA32_PKRS, 0, true); + vcpu->arch.cr3 = 0; kvm_register_mark_dirty(vcpu, VCPU_EXREG_CR3);
> + if (kvm_cpu_cap_has(X86_FEATURE_PKS)) { > + vcpu->arch.pkrs = pkrs; > + kvm_register_mark_available(vcpu, VCPU_EXREG_PKRS); > + vmcs_write64(GUEST_IA32_PKRS, pkrs); > + } > +}
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