From: Christian Borntraeger <borntraeger@de.ibm.com>
To: David Matlack <dmatlack@google.com>,
kvm@vger.kernel.org, Venkatesh Srinivas <venkateshs@chromium.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Andrew Jones <drjones@redhat.com>,
Ben Gardon <bgardon@google.com>, Peter Xu <peterx@redhat.com>
Subject: Re: [PATCH v2] KVM: selftests: Fix 32-bit truncation of vm_get_max_gfn()
Date: Tue, 8 Jun 2021 10:39:22 +0200 [thread overview]
Message-ID: <8cae6330-f88a-ec24-4e7d-bc999f49288d@de.ibm.com> (raw)
In-Reply-To: <20210521173828.1180619-1-dmatlack@google.com>
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 <venkateshs@chromium.org>
> Signed-off-by: David Matlack <dmatlack@google.com>
As a heads up:
I have not yet looked into this, but this broke demand_paging_test and kvm_page_table_test
on s390:
not ok 4 selftests: kvm: demand_paging_test # exit=254
# selftests: kvm: dirty_log_test
# ==== Test Assertion Failure ====
# lib/kvm_util.c:900: ret == 0
# pid=245410 tid=245410 errno=22 - Invalid argument
# 1 0x0000000001005457: vm_userspace_mem_region_add at kvm_util.c:900
# 2 0x0000000001002cbf: run_test at dirty_log_test.c:757
# 3 (inlined by) run_test at dirty_log_test.c:702
# 4 0x000000000100c055: for_each_guest_mode at guest_modes.c:37
# 5 0x00000000010022b5: main at dirty_log_test.c:929 (discriminator 3)
# 6 0x000003ff96fabdb3: ?? ??:0
# 7 0x000000000100241d: .annobin_lto.hot at crt1.o:?
# KVM_SET_USER_MEMORY_REGION IOCTL failed,
# rc: -1 errno: 22
# slot: 1 flags: 0x1
# guest_phys_addr: 0xfffffbfe00000 size: 0x40100000
# Test iterations: 32, interval: 10 (ms)
# Testing Log Mode 'dirty-log'
# Testing guest mode: PA-bits:52, VA-bits:48, 4K pages
# guest physical test memory offset: 0xfffffbfe00000
not ok 5 selftests: kvm: dirty_log_test # exit=254
# selftests: kvm: kvm_create_max_vcpus
# KVM_CAP_MAX_VCPU_ID: 248
# KVM_CAP_MAX_VCPUS: 248
# Testing creating 248 vCPUs, with IDs 0...247.
ok 6 selftests: kvm: kvm_create_max_vcpus
# selftests: kvm: kvm_page_table_test
# ==== Test Assertion Failure ====
# lib/kvm_util.c:900: ret == 0
# pid=245454 tid=245454 errno=22 - Invalid argument
# 1 0x0000000001003e47: vm_userspace_mem_region_add at kvm_util.c:900
# 2 0x000000000100257d: pre_init_before_test at kvm_page_table_test.c:302
# 3 (inlined by) run_test at kvm_page_table_test.c:374
# 4 0x000000000100aa45: for_each_guest_mode at guest_modes.c:37
# 5 0x0000000001001dd9: main at kvm_page_table_test.c:503
# 6 0x000003ff827abdb3: ?? ??:0
# 7 0x0000000001001e8d: .annobin_lto.hot at crt1.o:?
# KVM_SET_USER_MEMORY_REGION IOCTL failed,
# rc: -1 errno: 22
# slot: 1 flags: 0x0
# guest_phys_addr: 0xfffffbff00000 size: 0x40000000
not ok 7 selftests: kvm: kvm_page_table_test # exit=254
> ---
>
> 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 <inttypes.h>
>
> #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;
>
next prev parent reply other threads:[~2021-06-08 8:39 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-21 17:38 [PATCH v2] KVM: selftests: Fix 32-bit truncation of vm_get_max_gfn() David Matlack
2021-05-21 17:49 ` Peter Xu
2021-05-22 10:59 ` Andrew Jones
2021-05-24 12:30 ` Paolo Bonzini
2021-06-08 8:39 ` Christian Borntraeger [this message]
2021-06-08 10:03 ` Christian Borntraeger
2021-06-08 11:45 ` [PATCH] KVM: selftests: introduce P47V64 for s390x Christian Borntraeger
2021-06-08 11:49 ` Janosch Frank
2021-06-08 11:55 ` Christian Borntraeger
2021-06-08 12:18 ` Christian Borntraeger
2021-06-08 12:39 ` [PATCH v2] " Christian Borntraeger
2021-06-08 16:41 ` David Matlack
2021-06-08 17:19 ` Paolo Bonzini
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