When CONFIG_ARM64_POE is disabled, KVM does not save/restore POR_EL1. However, ID_AA64MMFR3_EL1 sanitisation currently exposes the feature to guests whenever the hardware supports it, ignoring the host kernel configuration. If a guest detects this feature and attempts to use it, the host will fail to context-switch POR_EL1, potentially leading to state corruption. Fix this by masking ID_AA64MMFR3_EL1.S1POE in the sanitised system registers, preventing KVM from advertising the feature when the host does not support it (i.e. system_supports_poe() is false). Fixes: 70ed7238297f ("KVM: arm64: Sanitise ID_AA64MMFR3_EL1") Signed-off-by: Fuad Tabba --- arch/arm64/kvm/sys_regs.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index 88a57ca36d96..237e8bd1cf29 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -1816,6 +1816,9 @@ static u64 __kvm_read_sanitised_id_reg(const struct kvm_vcpu *vcpu, ID_AA64MMFR3_EL1_SCTLRX | ID_AA64MMFR3_EL1_S1POE | ID_AA64MMFR3_EL1_S1PIE; + + if (!system_supports_poe()) + val &= ~ID_AA64MMFR3_EL1_S1POE; break; case SYS_ID_MMFR4_EL1: val &= ~ID_MMFR4_EL1_CCIDX; -- 2.53.0.273.g2a3d683680-goog Although ID register sanitisation prevents guests from seeing the feature, adding this check to the helper allows the compiler to entirely eliminate S1POE-specific code paths (such as context switching POR_EL1) when the host kernel is compiled without support (CONFIG_ARM64_POE is disabled). This aligns with the pattern used for other optional features like SVE (kvm_has_sve()) and FPMR (kvm_has_fpmr()), ensuring no POE logic if the host lacks support, regardless of the guest configuration state. Signed-off-by: Fuad Tabba --- arch/arm64/include/asm/kvm_host.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index ac7f970c7883..7af72ca749a6 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -1592,7 +1592,8 @@ void kvm_set_vm_id_reg(struct kvm *kvm, u32 reg, u64 val); (kvm_has_feat((k), ID_AA64MMFR3_EL1, S1PIE, IMP)) #define kvm_has_s1poe(k) \ - (kvm_has_feat((k), ID_AA64MMFR3_EL1, S1POE, IMP)) + (system_supports_poe() && \ + kvm_has_feat((k), ID_AA64MMFR3_EL1, S1POE, IMP)) #define kvm_has_ras(k) \ (kvm_has_feat((k), ID_AA64PFR0_EL1, RAS, IMP)) -- 2.53.0.273.g2a3d683680-goog In protected mode, the hypervisor maintains a separate instance of the `kvm` structure for each VM. For non-protected VMs, this structure is initialized from the host's `kvm` state. Currently, `pkvm_init_features_from_host()` copies the `KVM_ARCH_FLAG_ID_REGS_INITIALIZED` flag from the host without the underlying `id_regs` data being initialized. This results in the hypervisor seeing the flag as set while the ID registers remain zeroed. Consequently, `kvm_has_feat()` checks at EL2 fail (return 0) for non-protected VMs. This breaks logic that relies on feature detection, such as `ctxt_has_tcrx()` for TCR2_EL1 support. As a result, certain system registers (e.g., TCR2_EL1, PIR_EL1, POR_EL1) are not saved/restored during the world switch, which could lead to state corruption. Fix this by explicitly copying the ID registers from the host `kvm` to the hypervisor `kvm` for non-protected VMs during initialization, since we trust the host with its non-protected guests' features. Also ensure `KVM_ARCH_FLAG_ID_REGS_INITIALIZED` is cleared initially in `pkvm_init_features_from_host` so that `vm_copy_id_regs` can properly initialize them and set the flag once done. Fixes: 41d6028e28bd ("KVM: arm64: Convert the SVE guest vcpu flag to a vm flag") Signed-off-by: Fuad Tabba --- arch/arm64/kvm/hyp/nvhe/pkvm.c | 35 ++++++++++++++++++++++++++++++++-- 1 file changed, 33 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c index 12b2acfbcfd1..59a010221818 100644 --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c @@ -345,6 +345,7 @@ static void pkvm_init_features_from_host(struct pkvm_hyp_vm *hyp_vm, const struc /* No restrictions for non-protected VMs. */ if (!kvm_vm_is_protected(kvm)) { hyp_vm->kvm.arch.flags = host_arch_flags; + hyp_vm->kvm.arch.flags &= ~BIT_ULL(KVM_ARCH_FLAG_ID_REGS_INITIALIZED); bitmap_copy(kvm->arch.vcpu_features, host_kvm->arch.vcpu_features, @@ -471,6 +472,35 @@ static int pkvm_vcpu_init_sve(struct pkvm_hyp_vcpu *hyp_vcpu, struct kvm_vcpu *h return ret; } +static int vm_copy_id_regs(struct pkvm_hyp_vcpu *hyp_vcpu) +{ + struct pkvm_hyp_vm *hyp_vm = pkvm_hyp_vcpu_to_hyp_vm(hyp_vcpu); + const struct kvm *host_kvm = hyp_vm->host_kvm; + struct kvm *kvm = &hyp_vm->kvm; + + if (!test_bit(KVM_ARCH_FLAG_ID_REGS_INITIALIZED, &host_kvm->arch.flags)) + return -EINVAL; + + if (test_and_set_bit(KVM_ARCH_FLAG_ID_REGS_INITIALIZED, &kvm->arch.flags)) + return 0; + + memcpy(kvm->arch.id_regs, host_kvm->arch.id_regs, sizeof(kvm->arch.id_regs)); + + return 0; +} + +static int pkvm_vcpu_init_sysregs(struct pkvm_hyp_vcpu *hyp_vcpu) +{ + int ret = 0; + + if (pkvm_hyp_vcpu_is_protected(hyp_vcpu)) + kvm_init_pvm_id_regs(&hyp_vcpu->vcpu); + else + ret = vm_copy_id_regs(hyp_vcpu); + + return ret; +} + static int init_pkvm_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu, struct pkvm_hyp_vm *hyp_vm, struct kvm_vcpu *host_vcpu) @@ -490,8 +520,9 @@ static int init_pkvm_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu, hyp_vcpu->vcpu.arch.cflags = READ_ONCE(host_vcpu->arch.cflags); hyp_vcpu->vcpu.arch.mp_state.mp_state = KVM_MP_STATE_STOPPED; - if (pkvm_hyp_vcpu_is_protected(hyp_vcpu)) - kvm_init_pvm_id_regs(&hyp_vcpu->vcpu); + ret = pkvm_vcpu_init_sysregs(hyp_vcpu); + if (ret) + goto done; ret = pkvm_vcpu_init_traps(hyp_vcpu); if (ret) -- 2.53.0.273.g2a3d683680-goog The `sve_state` pointer in `hyp_vcpu->vcpu.arch` is initialized as a hypervisor virtual address during vCPU initialization in `pkvm_vcpu_init_sve()`. `unpin_host_sve_state()` calls `kern_hyp_va()` on this address. Since `kern_hyp_va()` is idempotent, it's not a bug. However, it is unnecessary and potentially confusing. Remove the redundant conversion. Signed-off-by: Fuad Tabba --- arch/arm64/kvm/hyp/nvhe/pkvm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c index 59a010221818..389fa5f09c3d 100644 --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c @@ -392,7 +392,7 @@ static void unpin_host_sve_state(struct pkvm_hyp_vcpu *hyp_vcpu) if (!vcpu_has_feature(&hyp_vcpu->vcpu, KVM_ARM_VCPU_SVE)) return; - sve_state = kern_hyp_va(hyp_vcpu->vcpu.arch.sve_state); + sve_state = hyp_vcpu->vcpu.arch.sve_state; hyp_unpin_shared_mem(sve_state, sve_state + vcpu_sve_state_size(&hyp_vcpu->vcpu)); } -- 2.53.0.273.g2a3d683680-goog