Re: [PATCH 2/5] KVM: selftests: add shmem backing source type

From: Ben Gardon
Date: Thu May 13 2021 - 17:46:34 EST

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On Wed, May 12, 2021 at 2:45 PM Axel Rasmussen <axelrasmussen@xxxxxxxxxx> wrote:
>
> This lets us run the demand paging test on top of a shmem-backed area.
> In follow-up commits, we'll 1) leverage this new capability to create an
> alias mapping, and then 2) use the alias mapping to exercise UFFD minor
> faults.
>
> Signed-off-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
> ---
> .../testing/selftests/kvm/include/test_util.h | 1 +
> tools/testing/selftests/kvm/lib/kvm_util.c | 24 ++++++++---
> tools/testing/selftests/kvm/lib/test_util.c | 40 +++++++++++--------
> 3 files changed, 44 insertions(+), 21 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
> index fade3130eb01..7377f00469ef 100644
> --- a/tools/testing/selftests/kvm/include/test_util.h
> +++ b/tools/testing/selftests/kvm/include/test_util.h
> @@ -84,6 +84,7 @@ enum vm_mem_backing_src_type {
> VM_MEM_SRC_ANONYMOUS_HUGETLB_1GB,
> VM_MEM_SRC_ANONYMOUS_HUGETLB_2GB,
> VM_MEM_SRC_ANONYMOUS_HUGETLB_16GB,
> + VM_MEM_SRC_SHMEM,
> NUM_SRC_TYPES,
> };
>
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index fc83f6c5902d..6fbe124e0e16 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -663,8 +663,8 @@ int kvm_memcmp_hva_gva(void *hva, struct kvm_vm *vm, vm_vaddr_t gva, size_t len)
> *
> * Input Args:
> * vm - Virtual Machine
> - * backing_src - Storage source for this region.
> - * NULL to use anonymous memory.
> + * src_type - Storage source for this region.
> + * NULL to use anonymous memory.

It would probably make sense to separate this rename out into a separate commit.

> * guest_paddr - Starting guest physical address
> * slot - KVM region slot
> * npages - Number of physical pages
> @@ -755,11 +755,25 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
> if (alignment > 1)
> region->mmap_size += alignment;
>
> + region->fd = -1;
> + if (src_type == VM_MEM_SRC_SHMEM) {
> + region->fd = memfd_create("kvm_selftest", MFD_CLOEXEC);
> + TEST_ASSERT(region->fd != -1,
> + "memfd_create failed, errno: %i", errno);
> +
> + ret = ftruncate(region->fd, region->mmap_size);
> + TEST_ASSERT(ret == 0, "ftruncate failed, errno: %i", errno);
> +
> + ret = fallocate(region->fd,
> + FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 0,
> + region->mmap_size);
> + TEST_ASSERT(ret == 0, "fallocate failed, errno: %i", errno);
> + }
> +
> region->mmap_start = mmap(NULL, region->mmap_size,
> PROT_READ | PROT_WRITE,
> - MAP_PRIVATE | MAP_ANONYMOUS
> - | vm_mem_backing_src_alias(src_type)->flag,
> - -1, 0);
> + vm_mem_backing_src_alias(src_type)->flag,
> + region->fd, 0);
> TEST_ASSERT(region->mmap_start != MAP_FAILED,
> "test_malloc failed, mmap_start: %p errno: %i",
> region->mmap_start, errno);
> diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
> index 63d2bc7d757b..c7a265da5090 100644
> --- a/tools/testing/selftests/kvm/lib/test_util.c
> +++ b/tools/testing/selftests/kvm/lib/test_util.c
> @@ -168,70 +168,77 @@ size_t get_def_hugetlb_pagesz(void)
>
> const struct vm_mem_backing_src_alias *vm_mem_backing_src_alias(uint32_t i)
> {
> + static const int anon_flags = MAP_PRIVATE | MAP_ANONYMOUS;
> + static const int anon_huge_flags = anon_flags | MAP_HUGETLB;
> +
> static const struct vm_mem_backing_src_alias aliases[] = {
> [VM_MEM_SRC_ANONYMOUS] = {
> .name = "anonymous",
> - .flag = 0,
> + .flag = anon_flags,

You could also do this refactoring in a separate commit, which would
make the change to support shmem quite small.

> },
> [VM_MEM_SRC_ANONYMOUS_THP] = {
> .name = "anonymous_thp",
> - .flag = 0,
> + .flag = anon_flags,
> },
> [VM_MEM_SRC_ANONYMOUS_HUGETLB] = {
> .name = "anonymous_hugetlb",
> - .flag = MAP_HUGETLB,
> + .flag = anon_huge_flags,
> },
> [VM_MEM_SRC_ANONYMOUS_HUGETLB_16KB] = {
> .name = "anonymous_hugetlb_16kb",
> - .flag = MAP_HUGETLB | MAP_HUGE_16KB,
> + .flag = anon_huge_flags | MAP_HUGE_16KB,
> },
> [VM_MEM_SRC_ANONYMOUS_HUGETLB_64KB] = {
> .name = "anonymous_hugetlb_64kb",
> - .flag = MAP_HUGETLB | MAP_HUGE_64KB,
> + .flag = anon_huge_flags | MAP_HUGE_64KB,
> },
> [VM_MEM_SRC_ANONYMOUS_HUGETLB_512KB] = {
> .name = "anonymous_hugetlb_512kb",
> - .flag = MAP_HUGETLB | MAP_HUGE_512KB,
> + .flag = anon_huge_flags | MAP_HUGE_512KB,
> },
> [VM_MEM_SRC_ANONYMOUS_HUGETLB_1MB] = {
> .name = "anonymous_hugetlb_1mb",
> - .flag = MAP_HUGETLB | MAP_HUGE_1MB,
> + .flag = anon_huge_flags | MAP_HUGE_1MB,
> },
> [VM_MEM_SRC_ANONYMOUS_HUGETLB_2MB] = {
> .name = "anonymous_hugetlb_2mb",
> - .flag = MAP_HUGETLB | MAP_HUGE_2MB,
> + .flag = anon_huge_flags | MAP_HUGE_2MB,
> },
> [VM_MEM_SRC_ANONYMOUS_HUGETLB_8MB] = {
> .name = "anonymous_hugetlb_8mb",
> - .flag = MAP_HUGETLB | MAP_HUGE_8MB,
> + .flag = anon_huge_flags | MAP_HUGE_8MB,
> },
> [VM_MEM_SRC_ANONYMOUS_HUGETLB_16MB] = {
> .name = "anonymous_hugetlb_16mb",
> - .flag = MAP_HUGETLB | MAP_HUGE_16MB,
> + .flag = anon_huge_flags | MAP_HUGE_16MB,
> },
> [VM_MEM_SRC_ANONYMOUS_HUGETLB_32MB] = {
> .name = "anonymous_hugetlb_32mb",
> - .flag = MAP_HUGETLB | MAP_HUGE_32MB,
> + .flag = anon_huge_flags | MAP_HUGE_32MB,
> },
> [VM_MEM_SRC_ANONYMOUS_HUGETLB_256MB] = {
> .name = "anonymous_hugetlb_256mb",
> - .flag = MAP_HUGETLB | MAP_HUGE_256MB,
> + .flag = anon_huge_flags | MAP_HUGE_256MB,
> },
> [VM_MEM_SRC_ANONYMOUS_HUGETLB_512MB] = {
> .name = "anonymous_hugetlb_512mb",
> - .flag = MAP_HUGETLB | MAP_HUGE_512MB,
> + .flag = anon_huge_flags | MAP_HUGE_512MB,
> },
> [VM_MEM_SRC_ANONYMOUS_HUGETLB_1GB] = {
> .name = "anonymous_hugetlb_1gb",
> - .flag = MAP_HUGETLB | MAP_HUGE_1GB,
> + .flag = anon_huge_flags | MAP_HUGE_1GB,
> },
> [VM_MEM_SRC_ANONYMOUS_HUGETLB_2GB] = {
> .name = "anonymous_hugetlb_2gb",
> - .flag = MAP_HUGETLB | MAP_HUGE_2GB,
> + .flag = anon_huge_flags | MAP_HUGE_2GB,
> },
> [VM_MEM_SRC_ANONYMOUS_HUGETLB_16GB] = {
> .name = "anonymous_hugetlb_16gb",
> - .flag = MAP_HUGETLB | MAP_HUGE_16GB,
> + .flag = anon_huge_flags | MAP_HUGE_16GB,
> + },
> + [VM_MEM_SRC_SHMEM] = {
> + .name = "shmem",
> + .flag = MAP_SHARED,
> },
> };
> _Static_assert(ARRAY_SIZE(aliases) == NUM_SRC_TYPES,
> @@ -250,6 +257,7 @@ size_t get_backing_src_pagesz(uint32_t i)
>
> switch (i) {
> case VM_MEM_SRC_ANONYMOUS:
> + case VM_MEM_SRC_SHMEM:
> return getpagesize();
> case VM_MEM_SRC_ANONYMOUS_THP:
> return get_trans_hugepagesz();
> --
> 2.31.1.607.g51e8a6a459-goog
>

Next message: Gustavo A. R. Silva: "[PATCH][next] bpf: Use struct_size() in kzalloc()"
Previous message: Stafford Horne: "Re: [PATCH 05/33] locking/atomic: openrisc: avoid asm-generic/atomic.h"
In reply to: Axel Rasmussen: "[PATCH 2/5] KVM: selftests: add shmem backing source type"
Next in thread: Axel Rasmussen: "[PATCH 3/5] KVM: selftests: create alias mappings when using shared memory"
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