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Thu, 11 Sep 2025 06:49:47 -0700 (PDT) Received: from f4d4888f22f2.ant.amazon.com.com ([15.248.2.27]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3e760778915sm2608361f8f.12.2025.09.11.06.49.46 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Thu, 11 Sep 2025 06:49:47 -0700 (PDT) From: Jack Thomson To: maz@kernel.org, oliver.upton@linux.dev, pbonzini@redhat.com Cc: joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, shuah@kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, isaku.yamahata@intel.com, roypat@amazon.co.uk, kalyazin@amazon.co.uk, jackabt@amazon.com Subject: [PATCH 3/6] KVM: arm64: Add pre_fault_memory implementation Date: Thu, 11 Sep 2025 14:46:45 +0100 Message-Id: <20250911134648.58945-4-jackabt.amazon@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <20250911134648.58945-1-jackabt.amazon@gmail.com> References: <20250911134648.58945-1-jackabt.amazon@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Jack Thomson Add kvm_arch_vcpu_pre_fault_memory() for arm64. The implementation hands off the stage-2 faulting logic to either gmem_abort() or user_mem_abort(). Update __gmem_abort() and __user_mem_abort() to take the pre_fault parameter. When passed, the paths to determine write or exec faults are short circuited to false, as when pre-faulting, it should be treated as a read fault. This closely follows the implementation on x86. Signed-off-by: Jack Thomson --- arch/arm64/kvm/Kconfig | 1 + arch/arm64/kvm/arm.c | 1 + arch/arm64/kvm/mmu.c | 71 ++++++++++++++++++++++++++++++++++++------ 3 files changed, 64 insertions(+), 9 deletions(-) diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig index bff62e75d681..1ac0605f86cb 100644 --- a/arch/arm64/kvm/Kconfig +++ b/arch/arm64/kvm/Kconfig @@ -25,6 +25,7 @@ menuconfig KVM select HAVE_KVM_CPU_RELAX_INTERCEPT select KVM_MMIO select KVM_GENERIC_DIRTYLOG_READ_PROTECT + select KVM_GENERIC_PRE_FAULT_MEMORY select KVM_XFER_TO_GUEST_WORK select KVM_VFIO select HAVE_KVM_DIRTY_RING_ACQ_REL diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 888f7c7abf54..65654a742864 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -322,6 +322,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long = ext) case KVM_CAP_IRQFD_RESAMPLE: case KVM_CAP_COUNTER_OFFSET: case KVM_CAP_ARM_WRITABLE_IMP_ID_REGS: + case KVM_CAP_PRE_FAULT_MEMORY: r =3D 1; break; case KVM_CAP_SET_GUEST_DEBUG2: diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 082e7d8ae655..002f564c6ac7 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1523,7 +1523,8 @@ static void adjust_nested_fault_perms(struct kvm_s2_t= rans *nested, =20 static int __gmem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, struct kvm_s2_trans *nested, - struct kvm_memory_slot *memslot, bool is_perm) + struct kvm_memory_slot *memslot, bool is_perm, + bool pre_fault) { bool write_fault, exec_fault, writable; enum kvm_pgtable_walk_flags flags =3D KVM_PGTABLE_WALK_MEMABORT_FLAGS; @@ -1537,6 +1538,9 @@ static int __gmem_abort(struct kvm_vcpu *vcpu, phys_a= ddr_t fault_ipa, gfn_t gfn; int ret; =20 + if (pre_fault) + flags |=3D KVM_PGTABLE_WALK_PRE_FAULT; + ret =3D prepare_mmu_memcache(vcpu, true, &memcache); if (ret) return ret; @@ -1546,8 +1550,8 @@ static int __gmem_abort(struct kvm_vcpu *vcpu, phys_a= ddr_t fault_ipa, else gfn =3D fault_ipa >> PAGE_SHIFT; =20 - write_fault =3D kvm_is_write_fault(vcpu); - exec_fault =3D kvm_vcpu_trap_is_exec_fault(vcpu); + write_fault =3D !pre_fault && kvm_is_write_fault(vcpu); + exec_fault =3D !pre_fault && kvm_vcpu_trap_is_exec_fault(vcpu); =20 VM_WARN_ON_ONCE(write_fault && exec_fault); =20 @@ -1599,7 +1603,7 @@ static int gmem_abort(struct kvm_vcpu *vcpu, phys_add= r_t fault_ipa, struct kvm_s2_trans *nested, struct kvm_memory_slot *memslot, bool is_perm) { - int ret =3D __gmem_abort(vcpu, fault_ipa, nested, memslot, is_perm); + int ret =3D __gmem_abort(vcpu, fault_ipa, nested, memslot, is_perm, false= ); return ret !=3D -EAGAIN ? ret : 0; } =20 @@ -1607,7 +1611,7 @@ static int __user_mem_abort(struct kvm_vcpu *vcpu, ph= ys_addr_t fault_ipa, struct kvm_s2_trans *nested, struct kvm_memory_slot *memslot, long *page_size, unsigned long hva, - bool fault_is_perm) + bool fault_is_perm, bool pre_fault) { int ret =3D 0; bool topup_memcache; @@ -1631,10 +1635,13 @@ static int __user_mem_abort(struct kvm_vcpu *vcpu, = phys_addr_t fault_ipa, vm_flags_t vm_flags; enum kvm_pgtable_walk_flags flags =3D KVM_PGTABLE_WALK_MEMABORT_FLAGS; =20 + if (pre_fault) + flags |=3D KVM_PGTABLE_WALK_PRE_FAULT; + if (fault_is_perm) fault_granule =3D kvm_vcpu_trap_get_perm_fault_granule(vcpu); - write_fault =3D kvm_is_write_fault(vcpu); - exec_fault =3D kvm_vcpu_trap_is_exec_fault(vcpu); + write_fault =3D !pre_fault && kvm_is_write_fault(vcpu); + exec_fault =3D !pre_fault && kvm_vcpu_trap_is_exec_fault(vcpu); VM_WARN_ON_ONCE(write_fault && exec_fault); =20 /* @@ -1895,8 +1902,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys= _addr_t fault_ipa, struct kvm_memory_slot *memslot, unsigned long hva, bool fault_is_perm) { - int ret =3D __user_mem_abort(vcpu, fault_ipa, nested, memslot, NULL, - hva, fault_is_perm); + int ret =3D __user_mem_abort(vcpu, fault_ipa, nested, memslot, NULL, hva, + fault_is_perm, false); return ret !=3D -EAGAIN ? ret : 0; } =20 @@ -2468,3 +2475,49 @@ void kvm_toggle_cache(struct kvm_vcpu *vcpu, bool wa= s_enabled) =20 trace_kvm_toggle_cache(*vcpu_pc(vcpu), was_enabled, now_enabled); } + +long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu, + struct kvm_pre_fault_memory *range) +{ + int r; + hva_t hva; + phys_addr_t end; + long page_size; + struct kvm_memory_slot *memslot; + phys_addr_t ipa =3D range->gpa; + gfn_t gfn =3D gpa_to_gfn(range->gpa); + + while (true) { + page_size =3D PAGE_SIZE; + memslot =3D gfn_to_memslot(vcpu->kvm, gfn); + if (!memslot) + return -ENOENT; + + if (kvm_slot_has_gmem(memslot)) { + r =3D __gmem_abort(vcpu, ipa, NULL, memslot, false, true); + } else { + hva =3D gfn_to_hva_memslot_prot(memslot, gfn, NULL); + if (kvm_is_error_hva(hva)) + return -EFAULT; + r =3D __user_mem_abort(vcpu, ipa, NULL, memslot, &page_size, hva, false, + true); + } + + if (r !=3D -EAGAIN) + break; + + if (signal_pending(current)) + return -EINTR; + + if (kvm_check_request(KVM_REQ_VM_DEAD, vcpu)) + return -EIO; + + cond_resched(); + }; + + if (r < 0) + return r; + + end =3D (range->gpa & ~(page_size - 1)) + page_size; + return min(range->size, end - range->gpa); +} --=20 2.43.0