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From: Oliver Upton To: Shaoqin Huang Cc: Marc Zyngier , kvmarm@lists.linux.dev, Eric Auger , Sebastian Ott , Cornelia Huck , James Morse , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Fuad Tabba , Mark Brown , Joey Gouly , Kristina Martsenko , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v1 1/2] KVM: arm64: Use kvm_has_feat() to check if FEAT_RAS is advertised to the guest Message-ID: References: <20240926032244.3666579-1-shahuang@redhat.com> <20240926032244.3666579-2-shahuang@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240926032244.3666579-2-shahuang@redhat.com> X-Migadu-Flow: FLOW_OUT On Wed, Sep 25, 2024 at 11:22:39PM -0400, Shaoqin Huang wrote: > diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c > index d7c2990e7c9e..99f256629ead 100644 > --- a/arch/arm64/kvm/handle_exit.c > +++ b/arch/arm64/kvm/handle_exit.c > @@ -405,7 +405,7 @@ int handle_exit(struct kvm_vcpu *vcpu, int exception_index) > void handle_exit_early(struct kvm_vcpu *vcpu, int exception_index) > { > if (ARM_SERROR_PENDING(exception_index)) { > - if (this_cpu_has_cap(ARM64_HAS_RAS_EXTN)) { > + if (kvm_has_feat(vcpu->kvm, ID_AA64PFR0_EL1, RAS, IMP)) { > u64 disr = kvm_vcpu_get_disr(vcpu); > > kvm_handle_guest_serror(vcpu, disr_to_esr(disr)); This is wrong; this is about handling *physical* SErrors, not virtual ones. So it really ought to be keyed off of the host cpucap. > diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h > index 37ff87d782b6..bf176a3cc594 100644 > --- a/arch/arm64/kvm/hyp/include/hyp/switch.h > +++ b/arch/arm64/kvm/hyp/include/hyp/switch.h > @@ -272,7 +272,7 @@ static inline void ___activate_traps(struct kvm_vcpu *vcpu, u64 hcr) > > write_sysreg(hcr, hcr_el2); > > - if (cpus_have_final_cap(ARM64_HAS_RAS_EXTN) && (hcr & HCR_VSE)) > + if (kvm_has_feat(vcpu->kvm, ID_AA64PFR0_EL1, RAS, IMP) && (hcr & HCR_VSE)) > write_sysreg_s(vcpu->arch.vsesr_el2, SYS_VSESR_EL2); > } I don't think this should be conditioned on guest visibility either. If FEAT_RAS is implemented in hardware, ESR_EL1 is set to the value of VSESR_EL2 when the vSError is taken, no matter what. > diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h > index 4c0fdabaf8ae..98526556d4e5 100644 > --- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h > +++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h > @@ -105,6 +105,8 @@ static inline void __sysreg_save_el1_state(struct kvm_cpu_context *ctxt) > > static inline void __sysreg_save_el2_return_state(struct kvm_cpu_context *ctxt) > { > + struct kvm_vcpu *vcpu = ctxt_to_vcpu(ctxt); > + > ctxt->regs.pc = read_sysreg_el2(SYS_ELR); > /* > * Guest PSTATE gets saved at guest fixup time in all > @@ -113,7 +115,7 @@ static inline void __sysreg_save_el2_return_state(struct kvm_cpu_context *ctxt) > if (!has_vhe() && ctxt->__hyp_running_vcpu) > ctxt->regs.pstate = read_sysreg_el2(SYS_SPSR); > > - if (cpus_have_final_cap(ARM64_HAS_RAS_EXTN)) > + if (kvm_has_feat(vcpu->kvm, ID_AA64PFR0_EL1, RAS, IMP)) > ctxt_sys_reg(ctxt, DISR_EL1) = read_sysreg_s(SYS_VDISR_EL2); > } > > @@ -220,6 +222,7 @@ static inline void __sysreg_restore_el2_return_state(struct kvm_cpu_context *ctx > { > u64 pstate = to_hw_pstate(ctxt); > u64 mode = pstate & PSR_AA32_MODE_MASK; > + struct kvm_vcpu *vcpu = ctxt_to_vcpu(ctxt); > > /* > * Safety check to ensure we're setting the CPU up to enter the guest > @@ -238,7 +241,7 @@ static inline void __sysreg_restore_el2_return_state(struct kvm_cpu_context *ctx > write_sysreg_el2(ctxt->regs.pc, SYS_ELR); > write_sysreg_el2(pstate, SYS_SPSR); > > - if (cpus_have_final_cap(ARM64_HAS_RAS_EXTN)) > + if (kvm_has_feat(vcpu->kvm, ID_AA64PFR0_EL1, RAS, IMP)) > write_sysreg_s(ctxt_sys_reg(ctxt, DISR_EL1), SYS_VDISR_EL2); > } These registers are still stateful no matter what, we cannot prevent an ESB instruction inside the VM from consuming a pending vSError. Keep in mind the ESB instruction is a NOP without FEAT_RAS, so it is still a legal instruction for a VM w/o FEAT_RAS. > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index 31e49da867ff..b09f8ba3525b 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -4513,7 +4513,7 @@ static void vcpu_set_hcr(struct kvm_vcpu *vcpu) > > if (has_vhe() || has_hvhe()) > vcpu->arch.hcr_el2 |= HCR_E2H; > - if (cpus_have_final_cap(ARM64_HAS_RAS_EXTN)) { > + if (kvm_has_feat(kvm, ID_AA64PFR0_EL1, RAS, IMP)) { > /* route synchronous external abort exceptions to EL2 */ > vcpu->arch.hcr_el2 |= HCR_TEA; > /* trap error record accesses */ No, we want external aborts to be taken to EL2. Wouldn't this also have the interesting property of allowing a VM w/o FEAT_RAS to access the error record registers? -- Thanks, Oliver