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AJvYcCX7N7/sv1WR+0b/uArL66XZnltTvPtaFWg5MIbIl1ocICxcHmwbbY+S1tCh/6rMG7jFkwBhHe8=@lists.linux.dev X-Gm-Message-State: AOJu0Yx0QVBBHnp/PYpcFVlhv9ygn/21ca/wdKORN6z9JStLjjcGWMj9 qV196AmErwpa1fgNMRm8056WHFbaZQ7xjZuS1ICGsguG0Ifa9LQL7krlmKCUzvAI0URRoaCT+zI I3A== X-Google-Smtp-Source: AGHT+IF7LN4zz7H7kl5hmHOJM2RWeLy8eWEca0zN52GnDIcb6JpxZKh2nX+K8PpdE1V0cGZIooZEsfLT5w== X-Received: from wmbdv17.prod.google.com ([2002:a05:600c:6211:b0:442:ea0c:c453]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:3107:b0:456:1752:2b44 with SMTP id 5b1f17b1804b1-45868d2fe87mr17408105e9.23.1753267654654; Wed, 23 Jul 2025 03:47:34 -0700 (PDT) Date: Wed, 23 Jul 2025 11:47:10 +0100 In-Reply-To: <20250723104714.1674617-1-tabba@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250723104714.1674617-1-tabba@google.com> X-Mailer: git-send-email 2.50.1.470.g6ba607880d-goog Message-ID: <20250723104714.1674617-19-tabba@google.com> Subject: [PATCH v16 18/22] KVM: arm64: nv: Handle VNCR_EL2-triggered faults backed by guest_memfd From: Fuad Tabba To: kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, kvmarm@lists.linux.dev Cc: pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, david@redhat.com, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com, ira.weiny@intel.com, tabba@google.com Content-Type: text/plain; charset="UTF-8" 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 --- 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: -- 2.50.1.470.g6ba607880d-goog