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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id o4sm9197317edq.25.2021.05.24.05.30.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 May 2021 05:30:36 -0700 (PDT) Subject: Re: [PATCH v2] KVM: selftests: Fix 32-bit truncation of vm_get_max_gfn() To: David Matlack , kvm@vger.kernel.org, Venkatesh Srinivas Cc: Andrew Jones , Ben Gardon , Peter Xu References: <20210521173828.1180619-1-dmatlack@google.com> From: Paolo Bonzini Message-ID: <59e09f4c-e844-4e84-24a2-30b485e05e78@redhat.com> Date: Mon, 24 May 2021 14:30:35 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210521173828.1180619-1-dmatlack@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 21/05/21 19:38, David Matlack wrote: > vm_get_max_gfn() casts vm->max_gfn from a uint64_t to an unsigned int, > which causes the upper 32-bits of the max_gfn to get truncated. > > Nobody noticed until now likely because vm_get_max_gfn() is only used > as a mechanism to create a memslot in an unused region of the guest > physical address space (the top), and the top of the 32-bit physical > address space was always good enough. > > This fix reveals a bug in memslot_modification_stress_test which was > trying to create a dummy memslot past the end of guest physical memory. > Fix that by moving the dummy memslot lower. > > Fixes: 52200d0d944e ("KVM: selftests: Remove duplicate guest mode handling") > Reviewed-by: Venkatesh Srinivas > Signed-off-by: David Matlack > --- > > v1 -> v2: > - Added Venkatesh's R-b line. > - Used PRIx64 to print uint64_t instead of %lx. > > tools/testing/selftests/kvm/include/kvm_util.h | 2 +- > tools/testing/selftests/kvm/lib/kvm_util.c | 2 +- > .../testing/selftests/kvm/lib/perf_test_util.c | 4 +++- > .../kvm/memslot_modification_stress_test.c | 18 +++++++++++------- > 4 files changed, 16 insertions(+), 10 deletions(-) > > diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h > index 84982eb02b29..5d9b35d09251 100644 > --- a/tools/testing/selftests/kvm/include/kvm_util.h > +++ b/tools/testing/selftests/kvm/include/kvm_util.h > @@ -303,7 +303,7 @@ bool vm_is_unrestricted_guest(struct kvm_vm *vm); > > unsigned int vm_get_page_size(struct kvm_vm *vm); > unsigned int vm_get_page_shift(struct kvm_vm *vm); > -unsigned int vm_get_max_gfn(struct kvm_vm *vm); > +uint64_t vm_get_max_gfn(struct kvm_vm *vm); > int vm_get_fd(struct kvm_vm *vm); > > unsigned int vm_calc_num_guest_pages(enum vm_guest_mode mode, size_t size); > diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c > index 1af1009254c4..aeffbb1e7c7d 100644 > --- a/tools/testing/selftests/kvm/lib/kvm_util.c > +++ b/tools/testing/selftests/kvm/lib/kvm_util.c > @@ -2058,7 +2058,7 @@ unsigned int vm_get_page_shift(struct kvm_vm *vm) > return vm->page_shift; > } > > -unsigned int vm_get_max_gfn(struct kvm_vm *vm) > +uint64_t vm_get_max_gfn(struct kvm_vm *vm) > { > return vm->max_gfn; > } > diff --git a/tools/testing/selftests/kvm/lib/perf_test_util.c b/tools/testing/selftests/kvm/lib/perf_test_util.c > index 81490b9b4e32..abf381800a59 100644 > --- a/tools/testing/selftests/kvm/lib/perf_test_util.c > +++ b/tools/testing/selftests/kvm/lib/perf_test_util.c > @@ -2,6 +2,7 @@ > /* > * Copyright (C) 2020, Google LLC. > */ > +#include > > #include "kvm_util.h" > #include "perf_test_util.h" > @@ -80,7 +81,8 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int vcpus, > */ > TEST_ASSERT(guest_num_pages < vm_get_max_gfn(vm), > "Requested more guest memory than address space allows.\n" > - " guest pages: %lx max gfn: %x vcpus: %d wss: %lx]\n", > + " guest pages: %" PRIx64 " max gfn: %" PRIx64 > + " vcpus: %d wss: %" PRIx64 "]\n", > guest_num_pages, vm_get_max_gfn(vm), vcpus, > vcpu_memory_bytes); > > diff --git a/tools/testing/selftests/kvm/memslot_modification_stress_test.c b/tools/testing/selftests/kvm/memslot_modification_stress_test.c > index 6096bf0a5b34..98351ba0933c 100644 > --- a/tools/testing/selftests/kvm/memslot_modification_stress_test.c > +++ b/tools/testing/selftests/kvm/memslot_modification_stress_test.c > @@ -71,14 +71,22 @@ struct memslot_antagonist_args { > }; > > static void add_remove_memslot(struct kvm_vm *vm, useconds_t delay, > - uint64_t nr_modifications, uint64_t gpa) > + uint64_t nr_modifications) > { > + const uint64_t pages = 1; > + uint64_t gpa; > int i; > > + /* > + * Add the dummy memslot just below the perf_test_util memslot, which is > + * at the top of the guest physical address space. > + */ > + gpa = guest_test_phys_mem - pages * vm_get_page_size(vm); > + > for (i = 0; i < nr_modifications; i++) { > usleep(delay); > vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, gpa, > - DUMMY_MEMSLOT_INDEX, 1, 0); > + DUMMY_MEMSLOT_INDEX, pages, 0); > > vm_mem_region_delete(vm, DUMMY_MEMSLOT_INDEX); > } > @@ -120,11 +128,7 @@ static void run_test(enum vm_guest_mode mode, void *arg) > pr_info("Started all vCPUs\n"); > > add_remove_memslot(vm, p->memslot_modification_delay, > - p->nr_memslot_modifications, > - guest_test_phys_mem + > - (guest_percpu_mem_size * nr_vcpus) + > - perf_test_args.host_page_size + > - perf_test_args.guest_page_size); > + p->nr_memslot_modifications); > > run_vcpus = false; > > Queued, thanks. Paolo