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Tue, 29 Jul 2025 15:56:04 -0700 (PDT) Reply-To: Sean Christopherson Date: Tue, 29 Jul 2025 15:54:50 -0700 In-Reply-To: <20250729225455.670324-1-seanjc@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250729225455.670324-1-seanjc@google.com> X-Mailer: git-send-email 2.50.1.552.g942d659e1b-goog Message-ID: <20250729225455.670324-20-seanjc@google.com> Subject: [PATCH v17 19/24] KVM: arm64: nv: Handle VNCR_EL2-triggered faults backed by guest_memfd From: Sean Christopherson To: Paolo Bonzini , Marc Zyngier , Oliver Upton , Sean Christopherson Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, Ira Weiny , Gavin Shan , Shivank Garg , Vlastimil Babka , Xiaoyao Li , David Hildenbrand , Fuad Tabba , Ackerley Tng , Tao Chan , James Houghton Content-Type: text/plain; charset="UTF-8" From: Fuad Tabba Handle faults for memslots backed by guest_memfd in arm64 nested virtualization triggered by VNCR_EL2. * Introduce is_gmem output parameter to kvm_translate_vncr(), indicating whether the faulted memory slot is backed by guest_memfd. * Dispatch faults backed by guest_memfd to kvm_gmem_get_pfn(). * Update kvm_handle_vncr_abort() to handle potential guest_memfd errors. Some of the guest_memfd errors need to be handled by userspace instead of attempting to (implicitly) retry by returning to the guest. Suggested-by: Marc Zyngier Reviewed-by: Marc Zyngier Signed-off-by: Fuad Tabba Signed-off-by: Sean Christopherson --- arch/arm64/kvm/nested.c | 41 +++++++++++++++++++++++++++++++++++------ 1 file changed, 35 insertions(+), 6 deletions(-) diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c index dc1d26559bfa..b3edd7f7c8cd 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -1172,8 +1172,9 @@ static u64 read_vncr_el2(struct kvm_vcpu *vcpu) return (u64)sign_extend64(__vcpu_sys_reg(vcpu, VNCR_EL2), 48); } -static int kvm_translate_vncr(struct kvm_vcpu *vcpu) +static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem) { + struct kvm_memory_slot *memslot; bool write_fault, writable; unsigned long mmu_seq; struct vncr_tlb *vt; @@ -1216,10 +1217,25 @@ static int kvm_translate_vncr(struct kvm_vcpu *vcpu) smp_rmb(); gfn = vt->wr.pa >> PAGE_SHIFT; - pfn = kvm_faultin_pfn(vcpu, gfn, write_fault, &writable, &page); - if (is_error_noslot_pfn(pfn) || (write_fault && !writable)) + memslot = gfn_to_memslot(vcpu->kvm, gfn); + if (!memslot) return -EFAULT; + *is_gmem = kvm_slot_has_gmem(memslot); + if (!*is_gmem) { + pfn = __kvm_faultin_pfn(memslot, gfn, write_fault ? FOLL_WRITE : 0, + &writable, &page); + if (is_error_noslot_pfn(pfn) || (write_fault && !writable)) + return -EFAULT; + } else { + ret = kvm_gmem_get_pfn(vcpu->kvm, memslot, gfn, &pfn, &page, NULL); + if (ret) { + kvm_prepare_memory_fault_exit(vcpu, vt->wr.pa, PAGE_SIZE, + write_fault, false, false); + return ret; + } + } + scoped_guard(write_lock, &vcpu->kvm->mmu_lock) { if (mmu_invalidate_retry(vcpu->kvm, mmu_seq)) return -EAGAIN; @@ -1292,23 +1308,36 @@ int kvm_handle_vncr_abort(struct kvm_vcpu *vcpu) if (esr_fsc_is_permission_fault(esr)) { inject_vncr_perm(vcpu); } else if (esr_fsc_is_translation_fault(esr)) { - bool valid; + bool valid, is_gmem = false; int ret; scoped_guard(read_lock, &vcpu->kvm->mmu_lock) valid = kvm_vncr_tlb_lookup(vcpu); if (!valid) - ret = kvm_translate_vncr(vcpu); + ret = kvm_translate_vncr(vcpu, &is_gmem); else ret = -EPERM; switch (ret) { case -EAGAIN: - case -ENOMEM: /* Let's try again... */ break; + case -ENOMEM: + /* + * For guest_memfd, this indicates that it failed to + * create a folio to back the memory. Inform userspace. + */ + if (is_gmem) + return 0; + /* Otherwise, let's try again... */ + break; case -EFAULT: + case -EIO: + case -EHWPOISON: + if (is_gmem) + return 0; + fallthrough; case -EINVAL: case -ENOENT: case -EACCES: -- 2.50.1.552.g942d659e1b-goog