2021-05-19 20:23:36

by Axel Rasmussen

Subject: [PATCH v2 07/10] KVM: selftests: add shmem backing source type

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 <[email protected]>
---
tools/testing/selftests/kvm/include/test_util.h | 1 +
tools/testing/selftests/kvm/lib/kvm_util.c | 15 +++++++++++++++
tools/testing/selftests/kvm/lib/test_util.c | 5 +++++
3 files changed, 21 insertions(+)

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 bc405785ac8b..e4a8d0c43c5e 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -757,6 +757,21 @@ 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,
vm_mem_backing_src_alias(src_type)->flag,
diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
index 06ddde068736..c7a265da5090 100644
--- a/tools/testing/selftests/kvm/lib/test_util.c
+++ b/tools/testing/selftests/kvm/lib/test_util.c
@@ -236,6 +236,10 @@ const struct vm_mem_backing_src_alias *vm_mem_backing_src_alias(uint32_t i)
.name = "anonymous_hugetlb_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,
"Missing new backing src types?");
@@ -253,6 +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();
--
2.31.1.751.gd2f1c929bd-goog

2021-05-19 22:06:06

by Ben Gardon

Subject: Re: [PATCH v2 07/10] KVM: selftests: add shmem backing source type

On Wed, May 19, 2021 at 1:04 PM Axel Rasmussen <[email protected]> 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 <[email protected]>
> ---
> tools/testing/selftests/kvm/include/test_util.h | 1 +
> tools/testing/selftests/kvm/lib/kvm_util.c | 15 +++++++++++++++
> tools/testing/selftests/kvm/lib/test_util.c | 5 +++++
> 3 files changed, 21 insertions(+)
>
> 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 bc405785ac8b..e4a8d0c43c5e 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -757,6 +757,21 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
> if (alignment > 1)
> region->mmap_size += alignment;
>
> + region->fd = -1;

Ah I guess this is the corresponding change from the previous patch.

> + 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,
> vm_mem_backing_src_alias(src_type)->flag,
> diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
> index 06ddde068736..c7a265da5090 100644
> --- a/tools/testing/selftests/kvm/lib/test_util.c
> +++ b/tools/testing/selftests/kvm/lib/test_util.c
> @@ -236,6 +236,10 @@ const struct vm_mem_backing_src_alias *vm_mem_backing_src_alias(uint32_t i)
> .name = "anonymous_hugetlb_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,
> "Missing new backing src types?");
> @@ -253,6 +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();
> --
> 2.31.1.751.gd2f1c929bd-goog
>