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Wed, 10 Jul 2024 16:42:47 -0700 (PDT) Date: Wed, 10 Jul 2024 23:42:14 +0000 In-Reply-To: <20240710234222.2333120-1-jthoughton@google.com> Mime-Version: 1.0 References: <20240710234222.2333120-1-jthoughton@google.com> X-Mailer: git-send-email 2.45.2.993.g49e7a77208-goog Message-ID: <20240710234222.2333120-11-jthoughton@google.com> Subject: [RFC PATCH 10/18] KVM: arm64: Add KVM Userfault support From: James Houghton To: Paolo Bonzini Cc: Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Zenghui Yu , Sean Christopherson , Shuah Khan , Peter Xu , Axel Rasmussen , David Matlack , James Houghton , kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240710_164249_943139_904062DF X-CRM114-Status: GOOD ( 17.36 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Support comes in three parts: 1. When KVM Userfault is enabled, only install PAGE_SIZE PTEs. This prevents us from being able to map a userfault-enabled pfn with a huge PTE in response to a fault on a non-userfault pfn. 2. When we get KVM_PFN_ERR_USERFAULT from __gfn_to_pfn_memslot, return a memory fault to userspace. 3. When KVM Userfault is enabled for a particular kvm_gfn_range, unmap it, so that we can get faults on it. Signed-off-by: James Houghton --- arch/arm64/kvm/Kconfig | 1 + arch/arm64/kvm/mmu.c | 36 ++++++++++++++++++++++++++++++++++-- 2 files changed, 35 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig index 58f09370d17e..358153d91d58 100644 --- a/arch/arm64/kvm/Kconfig +++ b/arch/arm64/kvm/Kconfig @@ -37,6 +37,7 @@ menuconfig KVM select HAVE_KVM_VCPU_RUN_PID_CHANGE select SCHED_INFO select GUEST_PERF_EVENTS if PERF_EVENTS + select KVM_USERFAULT help Support hosting virtualized guest machines. diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 8bcab0cc3fe9..ac283e606516 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1434,7 +1434,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, * logging_active is guaranteed to never be true for VM_PFNMAP * memslots. */ - if (logging_active) { + if (logging_active || kvm->userfault) { force_pte = true; vma_shift = PAGE_SHIFT; } else { @@ -1494,8 +1494,15 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, kvm_send_hwpoison_signal(hva, vma_shift); return 0; } - if (is_error_noslot_pfn(pfn)) + if (is_error_noslot_pfn(pfn)) { + if (pfn == KVM_PFN_ERR_USERFAULT) + kvm_prepare_memory_fault_exit(vcpu, gfn << PAGE_SHIFT, + PAGE_SIZE, write_fault, + /*exec=*/false, + /*private=*/false, + /*userfault=*/true); return -EFAULT; + } if (kvm_is_device_pfn(pfn)) { /* @@ -2105,3 +2112,28 @@ void kvm_toggle_cache(struct kvm_vcpu *vcpu, bool was_enabled) trace_kvm_toggle_cache(*vcpu_pc(vcpu), was_enabled, now_enabled); } + +#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES +bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm, + struct kvm_gfn_range *range) +{ + unsigned long attrs = range->arg.attributes; + + /* + * We only need to unmap if we're enabling userfault. Disabling it + * does not need an unmap. An unmap to get huge mappings will come + * later. + */ + if (attrs & KVM_MEMORY_ATTRIBUTE_USERFAULT) + kvm_unmap_gfn_range(kvm, range); + + return false; +} + +bool kvm_arch_post_set_memory_attributes(struct kvm *kvm, + struct kvm_gfn_range *range) +{ + /* Nothing to do! */ + return false; +} +#endif -- 2.45.2.993.g49e7a77208-goog