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V" , Emi Kisanuki , Vishal Annapurve , WeiLin.Chang@arm.com, Lorenzo Pieralisi Subject: Re: [PATCH v16 30/45] KVM: arm64: CCA: Handle realm vCPU load Message-ID: References: <20260803134403.80630-1-steven.price@arm.com> <20260803134403.80630-31-steven.price@arm.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260803134403.80630-31-steven.price@arm.com> On 08/03 14:43, Steven Price wrote: > When loading a realm VCPU much of the work is handled by the RMM so only > some of the actions are required. Rearrange kvm_arch_vcpu_load() > slightly so we can bail out early for a realm guest. Hi Steven, I found that Realm guests can execute WFI/WFE instructions without causing a REC exit, ignoring KVM's WFx trap policy. I'd suggest translating HCR_EL2.TWE/TWI into the corresponding run->enter.flags to honor the policy. Below is the patch I tested. ---- >From 8637cd6f818a3c56d8b898a72874e9485eb94e59 Mon Sep 17 00:00:00 2001 From: Kohei Enju Date: Mon, 10 Aug 2026 22:54:27 +0900 Subject: [PATCH] KVM: arm64: CCA: Honor WFx trap policy for Realm vCPUs Propagate KVM's WFx trap policy to the RMM by translating HCR_EL2.TWE/TWI into REC_ENTER TRAP_WFE/WFI flags before entering a REC. Without this, guests can execute WFE/WFI instructions without causing a REC exit, ignoring KVM's common trap policy. Configure the REC_ENTER flags to honor the policy. Signed-off-by: Kohei Enju --- arch/arm64/include/asm/kvm_rmi.h | 2 ++ arch/arm64/kvm/arm.c | 3 +++ arch/arm64/kvm/rmi.c | 14 ++++++++++++++ 3 files changed, 19 insertions(+) diff --git a/arch/arm64/include/asm/kvm_rmi.h b/arch/arm64/include/asm/kvm_rmi.h index 2789879b6701..b858c6b4db6a 100644 --- a/arch/arm64/include/asm/kvm_rmi.h +++ b/arch/arm64/include/asm/kvm_rmi.h @@ -109,6 +109,8 @@ void kvm_destroy_realm(struct kvm *kvm); int kvm_realm_teardown_stage2(struct kvm *kvm); void kvm_destroy_rec(struct kvm_vcpu *vcpu); +void kvm_rec_set_wfx_traps(struct kvm_vcpu *vcpu); + int kvm_rec_enter(struct kvm_vcpu *vcpu); int kvm_rec_exit(struct kvm_vcpu *vcpu, int rec_run_status); int kvm_rec_handle_request(struct kvm_vcpu *vcpu); diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 7edc572dd8ab..0cba333b4fd2 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -770,6 +770,9 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) else vcpu->arch.hcr_el2 |= HCR_TWI; + if (vcpu_is_rec(vcpu)) + kvm_rec_set_wfx_traps(vcpu); + vcpu_set_pauth_traps(vcpu); if (is_protected_kvm_enabled()) { diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c index c242dfc2c7a6..c472f3d03234 100644 --- a/arch/arm64/kvm/rmi.c +++ b/arch/arm64/kvm/rmi.c @@ -1302,6 +1302,20 @@ static void noinstr load_realm_timer_state(struct kvm_vcpu *vcpu) write_sysreg_el0(rec_exit->cntp_ctl, SYS_CNTP_CTL); } +void kvm_rec_set_wfx_traps(struct kvm_vcpu *vcpu) +{ + struct realm_rec *rec = &vcpu->arch.rec; + + rec->run->enter.flags &= + ~(REC_ENTER_FLAG_TRAP_WFE | REC_ENTER_FLAG_TRAP_WFI); + + if (vcpu->arch.hcr_el2 & HCR_TWE) + rec->run->enter.flags |= REC_ENTER_FLAG_TRAP_WFE; + + if (vcpu->arch.hcr_el2 & HCR_TWI) + rec->run->enter.flags |= REC_ENTER_FLAG_TRAP_WFI; +} + int noinstr kvm_rec_enter(struct kvm_vcpu *vcpu) { struct realm_rec *rec = &vcpu->arch.rec; -- 2.43.0 > > Signed-off-by: Steven Price > --- > arch/arm64/kvm/arm.c | 19 ++++++++++++------- > 1 file changed, 12 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index f1b26b263bf0..96e536d2dda8 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -707,7 +707,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) > struct kvm_s2_mmu *mmu; > int *last_ran; > > - if (is_protected_kvm_enabled()) > + if (is_protected_kvm_enabled() || kvm_is_realm(vcpu->kvm)) > goto nommu; > > if (vcpu_has_nv(vcpu)) > @@ -751,12 +751,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) > kvm_vgic_load(vcpu); > kvm_vcpu_load_debug(vcpu); > kvm_vcpu_load_fgt(vcpu); > - if (has_vhe()) > - kvm_vcpu_load_vhe(vcpu); > - kvm_arch_vcpu_load_fp(vcpu); > - kvm_vcpu_pmu_restore_guest(vcpu); > - if (kvm_arm_is_pvtime_enabled(&vcpu->arch)) > - kvm_make_request(KVM_REQ_RECORD_STEAL, vcpu); > > if (kvm_vcpu_should_clear_twe(vcpu)) > vcpu->arch.hcr_el2 &= ~HCR_TWE; > @@ -778,6 +772,17 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) > &vcpu->arch.vgic_cpu.vgic_v3); > } > > + /* No additional state needs to be loaded on Realmed VMs */ > + if (vcpu_is_rec(vcpu)) > + return; > + > + if (has_vhe()) > + kvm_vcpu_load_vhe(vcpu); > + kvm_arch_vcpu_load_fp(vcpu); > + kvm_vcpu_pmu_restore_guest(vcpu); > + if (kvm_arm_is_pvtime_enabled(&vcpu->arch)) > + kvm_make_request(KVM_REQ_RECORD_STEAL, vcpu); > + > if (!cpumask_test_cpu(cpu, vcpu->kvm->arch.supported_cpus)) > vcpu_set_on_unsupported_cpu(vcpu); > > -- > 2.43.0 >