From: Will Deacon Date: Mon, 30 Mar 2026 14:48:28 +0000 (+0100) Subject: KVM: arm64: Return -EFAULT from VCPU_RUN on access to a poisoned pte X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=5991916392d844ba6ed6c0d320ac6578f52e39b6;p=thirdparty%2Fkernel%2Flinux.git KVM: arm64: Return -EFAULT from VCPU_RUN on access to a poisoned pte If a protected vCPU faults on an IPA which appears to be mapped, query the hypervisor to determine whether or not the faulting pte has been poisoned by a forceful reclaim. If the pte has been poisoned, return -EFAULT back to userspace rather than retrying the instruction forever. Tested-by: Fuad Tabba Tested-by: Mostafa Saleh Signed-off-by: Will Deacon Link: https://patch.msgid.link/20260330144841.26181-28-will@kernel.org Signed-off-by: Marc Zyngier --- diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h index 04a230e906a76..6c79f7504d80f 100644 --- a/arch/arm64/include/asm/kvm_asm.h +++ b/arch/arm64/include/asm/kvm_asm.h @@ -90,6 +90,7 @@ enum __kvm_host_smccc_func { __KVM_HOST_SMCCC_FUNC___pkvm_unreserve_vm, __KVM_HOST_SMCCC_FUNC___pkvm_init_vm, __KVM_HOST_SMCCC_FUNC___pkvm_init_vcpu, + __KVM_HOST_SMCCC_FUNC___pkvm_vcpu_in_poison_fault, __KVM_HOST_SMCCC_FUNC___pkvm_force_reclaim_guest_page, __KVM_HOST_SMCCC_FUNC___pkvm_reclaim_dying_guest_page, __KVM_HOST_SMCCC_FUNC___pkvm_start_teardown_vm, diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h index acc0311036004..8bc9a2489298d 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h @@ -40,6 +40,7 @@ int __pkvm_hyp_donate_host(u64 pfn, u64 nr_pages); int __pkvm_host_share_ffa(u64 pfn, u64 nr_pages); int __pkvm_host_unshare_ffa(u64 pfn, u64 nr_pages); int __pkvm_host_donate_guest(u64 pfn, u64 gfn, struct pkvm_hyp_vcpu *vcpu); +int __pkvm_vcpu_in_poison_fault(struct pkvm_hyp_vcpu *hyp_vcpu); int __pkvm_host_force_reclaim_page_guest(phys_addr_t phys); int __pkvm_host_reclaim_page_guest(u64 gfn, struct pkvm_hyp_vm *vm); int __pkvm_host_share_guest(u64 pfn, u64 gfn, u64 nr_pages, struct pkvm_hyp_vcpu *vcpu, diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c index 456c832077173..90e3b14fe2879 100644 --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c @@ -573,6 +573,15 @@ static void handle___pkvm_init_vcpu(struct kvm_cpu_context *host_ctxt) cpu_reg(host_ctxt, 1) = __pkvm_init_vcpu(handle, host_vcpu, vcpu_hva); } +static void handle___pkvm_vcpu_in_poison_fault(struct kvm_cpu_context *host_ctxt) +{ + int ret; + struct pkvm_hyp_vcpu *hyp_vcpu = pkvm_get_loaded_hyp_vcpu(); + + ret = hyp_vcpu ? __pkvm_vcpu_in_poison_fault(hyp_vcpu) : -EINVAL; + cpu_reg(host_ctxt, 1) = ret; +} + static void handle___pkvm_force_reclaim_guest_page(struct kvm_cpu_context *host_ctxt) { DECLARE_REG(phys_addr_t, phys, host_ctxt, 1); @@ -641,6 +650,7 @@ static const hcall_t host_hcall[] = { HANDLE_FUNC(__pkvm_unreserve_vm), HANDLE_FUNC(__pkvm_init_vm), HANDLE_FUNC(__pkvm_init_vcpu), + HANDLE_FUNC(__pkvm_vcpu_in_poison_fault), HANDLE_FUNC(__pkvm_force_reclaim_guest_page), HANDLE_FUNC(__pkvm_reclaim_dying_guest_page), HANDLE_FUNC(__pkvm_start_teardown_vm), diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c index 73bdbd4a508ee..31ca3db26fb5a 100644 --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c @@ -890,6 +890,49 @@ static int get_valid_guest_pte(struct pkvm_hyp_vm *vm, u64 ipa, kvm_pte_t *ptep, return 0; } +int __pkvm_vcpu_in_poison_fault(struct pkvm_hyp_vcpu *hyp_vcpu) +{ + struct pkvm_hyp_vm *vm = pkvm_hyp_vcpu_to_hyp_vm(hyp_vcpu); + kvm_pte_t pte; + s8 level; + u64 ipa; + int ret; + + switch (kvm_vcpu_trap_get_class(&hyp_vcpu->vcpu)) { + case ESR_ELx_EC_DABT_LOW: + case ESR_ELx_EC_IABT_LOW: + if (kvm_vcpu_trap_is_translation_fault(&hyp_vcpu->vcpu)) + break; + fallthrough; + default: + return -EINVAL; + } + + /* + * The host has the faulting IPA when it calls us from the guest + * fault handler but we retrieve it ourselves from the FAR so as + * to avoid exposing an "oracle" that could reveal data access + * patterns of the guest after initial donation of its pages. + */ + ipa = kvm_vcpu_get_fault_ipa(&hyp_vcpu->vcpu); + ipa |= FAR_TO_FIPA_OFFSET(kvm_vcpu_get_hfar(&hyp_vcpu->vcpu)); + + guest_lock_component(vm); + ret = kvm_pgtable_get_leaf(&vm->pgt, ipa, &pte, &level); + if (ret) + goto unlock; + + if (level != KVM_PGTABLE_LAST_LEVEL) { + ret = -EINVAL; + goto unlock; + } + + ret = guest_pte_is_poisoned(pte); +unlock: + guest_unlock_component(vm); + return ret; +} + int __pkvm_host_share_hyp(u64 pfn) { u64 phys = hyp_pfn_to_phys(pfn); diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c index 10edd49659362..7f35df29e9848 100644 --- a/arch/arm64/kvm/pkvm.c +++ b/arch/arm64/kvm/pkvm.c @@ -423,10 +423,13 @@ int pkvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size, return -EINVAL; /* - * We raced with another vCPU. + * We either raced with another vCPU or the guest PTE + * has been poisoned by an erroneous host access. */ - if (mapping) - return -EAGAIN; + if (mapping) { + ret = kvm_call_hyp_nvhe(__pkvm_vcpu_in_poison_fault); + return ret ? -EFAULT : -EAGAIN; + } ret = kvm_call_hyp_nvhe(__pkvm_host_donate_guest, pfn, gfn); } else {