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Wed, 19 Nov 2025 07:49:30 -0800 (PST) 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, xmarcalx@amazon.co.uk, kalyazin@amazon.co.uk, jackabt@amazon.com Subject: [PATCH v3 1/3] KVM: arm64: Add pre_fault_memory implementation Date: Wed, 19 Nov 2025 15:49:08 +0000 Message-ID: <20251119154910.97716-2-jackabt.amazon@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20251119154910.97716-1-jackabt.amazon@gmail.com> References: <20251119154910.97716-1-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(). Add an optional page_size output parameter to user_mem_abort() to return the VMA page size, which is needed when pre-faulting. Update the documentation to clarify x86 specific behaviour. Signed-off-by: Jack Thomson Tested-by: Vladimir Murzin --- Documentation/virt/kvm/api.rst | 3 +- arch/arm64/kvm/Kconfig | 1 + arch/arm64/kvm/arm.c | 1 + arch/arm64/kvm/mmu.c | 73 ++++++++++++++++++++++++++++++++-- 4 files changed, 73 insertions(+), 5 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 57061fa29e6a..30872d080511 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6493,7 +6493,8 @@ Errors: KVM_PRE_FAULT_MEMORY populates KVM's stage-2 page tables used to map memory for the current vCPU state. KVM maps memory as if the vCPU generated a stage-2 read page fault, e.g. faults in memory as needed, but doesn't break -CoW. However, KVM does not mark any newly created stage-2 PTE as Accessed. +CoW. However, on x86, KVM does not mark any newly created stage-2 PTE as +Accessed. =20 In the case of confidential VM types where there is an initial set up of private guest memory before the guest is 'finalized'/measured, this ioctl diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig index 4f803fd1c99a..6872aaabe16c 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 VIRT_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 870953b4a8a7..88c5dc2b4ee8 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -327,6 +327,7 @@ 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 7cc964af8d30..cba09168fc6d 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1599,8 +1599,8 @@ static int gmem_abort(struct kvm_vcpu *vcpu, phys_add= r_t fault_ipa, =20 static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, struct kvm_s2_trans *nested, - struct kvm_memory_slot *memslot, unsigned long hva, - bool fault_is_perm) + struct kvm_memory_slot *memslot, long *page_size, + unsigned long hva, bool fault_is_perm) { int ret =3D 0; bool topup_memcache; @@ -1878,6 +1878,9 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys= _addr_t fault_ipa, kvm_release_faultin_page(kvm, page, !!ret, writable); kvm_fault_unlock(kvm); =20 + if (page_size) + *page_size =3D vma_pagesize; + /* Mark the page dirty only if the fault is handled successfully */ if (writable && !ret) mark_page_dirty_in_slot(kvm, memslot, gfn); @@ -2080,8 +2083,8 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu) ret =3D gmem_abort(vcpu, fault_ipa, nested, memslot, esr_fsc_is_permission_fault(esr)); else - ret =3D user_mem_abort(vcpu, fault_ipa, nested, memslot, hva, - esr_fsc_is_permission_fault(esr)); + ret =3D user_mem_abort(vcpu, fault_ipa, nested, memslot, NULL, + hva, esr_fsc_is_permission_fault(esr)); if (ret =3D=3D 0) ret =3D 1; out: @@ -2457,3 +2460,65 @@ 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 ret, idx; + hva_t hva; + phys_addr_t end; + struct kvm_memory_slot *memslot; + struct kvm_vcpu_fault_info stored_fault, *fault_info; + + long page_size =3D PAGE_SIZE; + phys_addr_t ipa =3D range->gpa; + gfn_t gfn =3D gpa_to_gfn(range->gpa); + + idx =3D srcu_read_lock(&vcpu->kvm->srcu); + + if (ipa >=3D kvm_phys_size(vcpu->arch.hw_mmu)) { + ret =3D -ENOENT; + goto out_unlock; + } + + memslot =3D gfn_to_memslot(vcpu->kvm, gfn); + if (!memslot) { + ret =3D -ENOENT; + goto out_unlock; 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Wed, 19 Nov 2025 07:49:33 -0800 (PST) Received: from f4d4888f22f2.ant.amazon.com.com ([15.248.3.91]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-42c9628ebacsm25969755f8f.30.2025.11.19.07.49.32 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 19 Nov 2025 07:49:33 -0800 (PST) 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, xmarcalx@amazon.co.uk, kalyazin@amazon.co.uk, jackabt@amazon.com Subject: [PATCH v3 2/3] KVM: selftests: Enable pre_fault_memory_test for arm64 Date: Wed, 19 Nov 2025 15:49:09 +0000 Message-ID: <20251119154910.97716-3-jackabt.amazon@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20251119154910.97716-1-jackabt.amazon@gmail.com> References: <20251119154910.97716-1-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 Enable the pre_fault_memory_test to run on arm64 by making it work with different guest page sizes and testing multiple guest configurations. Update the test_assert to compare against the UCALL_EXIT_REASON, for portability, as arm64 exits with KVM_EXIT_MMIO while x86 uses KVM_EXIT_IO. Signed-off-by: Jack Thomson --- tools/testing/selftests/kvm/Makefile.kvm | 1 + .../selftests/kvm/pre_fault_memory_test.c | 78 ++++++++++++++----- 2 files changed, 58 insertions(+), 21 deletions(-) diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selft= ests/kvm/Makefile.kvm index 148d427ff24b..0ddd8db60197 100644 --- a/tools/testing/selftests/kvm/Makefile.kvm +++ b/tools/testing/selftests/kvm/Makefile.kvm @@ -183,6 +183,7 @@ TEST_GEN_PROGS_arm64 +=3D memslot_perf_test TEST_GEN_PROGS_arm64 +=3D mmu_stress_test TEST_GEN_PROGS_arm64 +=3D rseq_test TEST_GEN_PROGS_arm64 +=3D steal_time +TEST_GEN_PROGS_arm64 +=3D pre_fault_memory_test =20 TEST_GEN_PROGS_s390 =3D $(TEST_GEN_PROGS_COMMON) TEST_GEN_PROGS_s390 +=3D s390/memop diff --git a/tools/testing/selftests/kvm/pre_fault_memory_test.c b/tools/te= sting/selftests/kvm/pre_fault_memory_test.c index f04768c1d2e4..674931e7bb3a 100644 --- a/tools/testing/selftests/kvm/pre_fault_memory_test.c +++ b/tools/testing/selftests/kvm/pre_fault_memory_test.c @@ -11,19 +11,29 @@ #include #include #include +#include =20 /* Arbitrarily chosen values */ -#define TEST_SIZE (SZ_2M + PAGE_SIZE) -#define TEST_NPAGES (TEST_SIZE / PAGE_SIZE) +#define TEST_BASE_SIZE SZ_2M #define TEST_SLOT 10 =20 +/* Storage of test info to share with guest code */ +struct test_config { + int page_size; + uint64_t test_size; + uint64_t test_num_pages; +}; + +struct test_config test_config; + static void guest_code(uint64_t base_gpa) { volatile uint64_t val __used; + struct test_config *config =3D &test_config; int i; =20 - for (i =3D 0; i < TEST_NPAGES; i++) { - uint64_t *src =3D (uint64_t *)(base_gpa + i * PAGE_SIZE); + for (i =3D 0; i < config->test_num_pages; i++) { + uint64_t *src =3D (uint64_t *)(base_gpa + i * config->page_size); =20 val =3D *src; } @@ -159,11 +169,17 @@ static void pre_fault_memory(struct kvm_vcpu *vcpu, u= 64 base_gpa, u64 offset, KVM_PRE_FAULT_MEMORY, ret, vcpu->vm); } =20 -static void __test_pre_fault_memory(unsigned long vm_type, bool private) +struct test_params { + unsigned long vm_type; + bool private; +}; + +static void __test_pre_fault_memory(enum vm_guest_mode guest_mode, void *a= rg) { + struct test_params *p =3D arg; const struct vm_shape shape =3D { - .mode =3D VM_MODE_DEFAULT, - .type =3D vm_type, + .mode =3D guest_mode, + .type =3D p->vm_type, }; struct kvm_vcpu *vcpu; struct kvm_run *run; @@ -174,10 +190,17 @@ static void __test_pre_fault_memory(unsigned long vm_= type, bool private) uint64_t guest_test_virt_mem; uint64_t alignment, guest_page_size; =20 + pr_info("Testing guest mode: %s\n", vm_guest_mode_string(guest_mode)); + vm =3D vm_create_shape_with_one_vcpu(shape, &vcpu, guest_code); =20 - alignment =3D guest_page_size =3D vm_guest_mode_params[VM_MODE_DEFAULT].p= age_size; - guest_test_phys_mem =3D (vm->max_gfn - TEST_NPAGES) * guest_page_size; + guest_page_size =3D vm_guest_mode_params[guest_mode].page_size; + + test_config.page_size =3D guest_page_size; + test_config.test_size =3D TEST_BASE_SIZE + test_config.page_size; + test_config.test_num_pages =3D vm_calc_num_guest_pages(vm->mode, test_con= fig.test_size); + + guest_test_phys_mem =3D (vm->max_gfn - test_config.test_num_pages) * test= _config.page_size; #ifdef __s390x__ alignment =3D max(0x100000UL, guest_page_size); #else @@ -187,23 +210,31 @@ static void __test_pre_fault_memory(unsigned long vm_= type, bool private) guest_test_virt_mem =3D guest_test_phys_mem & ((1ULL << (vm->va_bits - 1)= ) - 1); =20 vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, - guest_test_phys_mem, TEST_SLOT, TEST_NPAGES, - private ? KVM_MEM_GUEST_MEMFD : 0); - virt_map(vm, guest_test_virt_mem, guest_test_phys_mem, TEST_NPAGES); + guest_test_phys_mem, TEST_SLOT, test_config.test_num_pages, + p->private ? KVM_MEM_GUEST_MEMFD : 0); + virt_map(vm, guest_test_virt_mem, guest_test_phys_mem, test_config.test_n= um_pages); + + if (p->private) + vm_mem_set_private(vm, guest_test_phys_mem, test_config.test_size); + pre_fault_memory(vcpu, guest_test_phys_mem, TEST_BASE_SIZE, 0, p->private= ); + /* Test pre-faulting over an already faulted range */ + pre_fault_memory(vcpu, guest_test_phys_mem, TEST_BASE_SIZE, 0, p->private= ); + pre_fault_memory(vcpu, guest_test_phys_mem + TEST_BASE_SIZE, + test_config.page_size * 2, test_config.page_size, p->private); + pre_fault_memory(vcpu, guest_test_phys_mem + test_config.test_size, + test_config.page_size, test_config.page_size, p->private); =20 - if (private) - vm_mem_set_private(vm, guest_test_phys_mem, TEST_SIZE); + vcpu_args_set(vcpu, 1, guest_test_virt_mem); =20 - pre_fault_memory(vcpu, guest_test_phys_mem, 0, SZ_2M, 0, private); - pre_fault_memory(vcpu, guest_test_phys_mem, SZ_2M, PAGE_SIZE * 2, PAGE_SI= ZE, private); - pre_fault_memory(vcpu, guest_test_phys_mem, TEST_SIZE, PAGE_SIZE, PAGE_SI= ZE, private); 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Wed, 19 Nov 2025 07:49:36 -0800 (PST) Received: from f4d4888f22f2.ant.amazon.com.com ([15.248.3.91]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-42c9628ebacsm25969755f8f.30.2025.11.19.07.49.35 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 19 Nov 2025 07:49:36 -0800 (PST) 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, xmarcalx@amazon.co.uk, kalyazin@amazon.co.uk, jackabt@amazon.com Subject: [PATCH v3 3/3] KVM: selftests: Add option for different backing in pre-fault tests Date: Wed, 19 Nov 2025 15:49:10 +0000 Message-ID: <20251119154910.97716-4-jackabt.amazon@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20251119154910.97716-1-jackabt.amazon@gmail.com> References: <20251119154910.97716-1-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 a -m option to specify different memory backing types for the pre-fault tests (e.g., anonymous, hugetlb), allowing testing of the pre-fault functionality across different memory configurations. Signed-off-by: Jack Thomson --- .../selftests/kvm/pre_fault_memory_test.c | 42 +++++++++++++++---- 1 file changed, 33 insertions(+), 9 deletions(-) diff --git a/tools/testing/selftests/kvm/pre_fault_memory_test.c b/tools/te= sting/selftests/kvm/pre_fault_memory_test.c index 674931e7bb3a..e1111c4df748 100644 --- a/tools/testing/selftests/kvm/pre_fault_memory_test.c +++ b/tools/testing/selftests/kvm/pre_fault_memory_test.c @@ -172,6 +172,7 @@ static void pre_fault_memory(struct kvm_vcpu *vcpu, u64= base_gpa, u64 offset, struct test_params { unsigned long vm_type; bool private; + enum vm_mem_backing_src_type mem_backing_src; }; =20 static void __test_pre_fault_memory(enum vm_guest_mode guest_mode, void *a= rg) @@ -190,14 +191,19 @@ static void __test_pre_fault_memory(enum vm_guest_mod= e guest_mode, void *arg) uint64_t guest_test_virt_mem; uint64_t alignment, guest_page_size; =20 + size_t backing_src_pagesz =3D get_backing_src_pagesz(p->mem_backing_src); + pr_info("Testing guest mode: %s\n", vm_guest_mode_string(guest_mode)); + pr_info("Testing memory backing src type: %s\n", + vm_mem_backing_src_alias(p->mem_backing_src)->name); =20 vm =3D vm_create_shape_with_one_vcpu(shape, &vcpu, guest_code); =20 guest_page_size =3D vm_guest_mode_params[guest_mode].page_size; =20 test_config.page_size =3D guest_page_size; - test_config.test_size =3D TEST_BASE_SIZE + test_config.page_size; + test_config.test_size =3D align_up(TEST_BASE_SIZE + test_config.page_size, + backing_src_pagesz); test_config.test_num_pages =3D vm_calc_num_guest_pages(vm->mode, test_con= fig.test_size); =20 guest_test_phys_mem =3D (vm->max_gfn - test_config.test_num_pages) * test= _config.page_size; @@ -206,20 +212,23 @@ static void __test_pre_fault_memory(enum vm_guest_mod= e guest_mode, void *arg) #else alignment =3D SZ_2M; #endif + alignment =3D max(alignment, backing_src_pagesz); guest_test_phys_mem =3D align_down(guest_test_phys_mem, alignment); guest_test_virt_mem =3D guest_test_phys_mem & ((1ULL << (vm->va_bits - 1)= ) - 1); =20 - vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, + vm_userspace_mem_region_add(vm, p->mem_backing_src, guest_test_phys_mem, TEST_SLOT, test_config.test_num_pages, p->private ? KVM_MEM_GUEST_MEMFD : 0); virt_map(vm, guest_test_virt_mem, guest_test_phys_mem, test_config.test_n= um_pages); =20 if (p->private) vm_mem_set_private(vm, guest_test_phys_mem, test_config.test_size); - pre_fault_memory(vcpu, guest_test_phys_mem, TEST_BASE_SIZE, 0, p->private= ); + + pre_fault_memory(vcpu, guest_test_phys_mem, test_config.test_size, 0, p->= private); /* Test pre-faulting over an already faulted range */ - pre_fault_memory(vcpu, guest_test_phys_mem, TEST_BASE_SIZE, 0, p->private= ); - pre_fault_memory(vcpu, guest_test_phys_mem + TEST_BASE_SIZE, + pre_fault_memory(vcpu, guest_test_phys_mem, test_config.test_size, 0, p->= private); + pre_fault_memory(vcpu, guest_test_phys_mem + + test_config.test_size - test_config.page_size, test_config.page_size * 2, test_config.page_size, p->private); pre_fault_memory(vcpu, guest_test_phys_mem + test_config.test_size, test_config.page_size, test_config.page_size, p->private); @@ -251,7 +260,8 @@ static void __test_pre_fault_memory(enum vm_guest_mode = guest_mode, void *arg) kvm_vm_free(vm); } =20 -static void test_pre_fault_memory(unsigned long vm_type, bool private) +static void test_pre_fault_memory(unsigned long vm_type, enum vm_mem_backi= ng_src_type backing_src, + bool private) { if (vm_type && !(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(vm_type))) { pr_info("Skipping tests for vm_type 0x%lx\n", vm_type); @@ -261,6 +271,7 @@ static void test_pre_fault_memory(unsigned long vm_type= , bool private) struct test_params p =3D { .vm_type =3D vm_type, .private =3D private, + .mem_backing_src =3D backing_src, }; =20 for_each_guest_mode(__test_pre_fault_memory, &p); @@ -270,10 +281,23 @@ int main(int argc, char *argv[]) { TEST_REQUIRE(kvm_check_cap(KVM_CAP_PRE_FAULT_MEMORY)); =20 - test_pre_fault_memory(0, false); + int opt; + enum vm_mem_backing_src_type backing =3D VM_MEM_SRC_ANONYMOUS; + + while ((opt =3D getopt(argc, argv, "m:")) !=3D -1) { + switch (opt) { + case 'm': + backing =3D parse_backing_src_type(optarg); + break; + default: + break; + } + } + + test_pre_fault_memory(0, backing, false); #ifdef __x86_64__ - test_pre_fault_memory(KVM_X86_SW_PROTECTED_VM, false); - test_pre_fault_memory(KVM_X86_SW_PROTECTED_VM, true); + test_pre_fault_memory(KVM_X86_SW_PROTECTED_VM, backing, false); + test_pre_fault_memory(KVM_X86_SW_PROTECTED_VM, backing, true); #endif return 0; } --=20 2.43.0