On Sun, Nov 5, 2023 at 4:34 PM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> From: Vishal Annapurve <vannapurve@google.com>
>
> Add helpers to convert memory between private and shared via KVM's
> memory attributes, as well as helpers to free/allocate guest_memfd memory
> via fallocate(). Userspace, i.e. tests, is NOT required to do fallocate()
> when converting memory, as the attributes are the single source of true.
nit: true->truth
> Provide allocate() helpers so that tests can mimic a userspace that frees
> private memory on conversion, e.g. to prioritize memory usage over
> performance.
>
> Signed-off-by: Vishal Annapurve <vannapurve@google.com>
> Co-developed-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> Message-Id: <20231027182217.3615211-28-seanjc@google.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> .../selftests/kvm/include/kvm_util_base.h | 48 +++++++++++++++++++
> tools/testing/selftests/kvm/lib/kvm_util.c | 28 +++++++++++
> 2 files changed, 76 insertions(+)
>
> diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
> index 9f861182c02a..1441fca6c273 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util_base.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
> @@ -333,6 +333,54 @@ static inline void vm_enable_cap(struct kvm_vm *vm, uint32_t cap, uint64_t arg0)
> vm_ioctl(vm, KVM_ENABLE_CAP, &enable_cap);
> }
>
> +static inline void vm_set_memory_attributes(struct kvm_vm *vm, uint64_t gpa,
> + uint64_t size, uint64_t attributes)
> +{
> + struct kvm_memory_attributes attr = {
> + .attributes = attributes,
> + .address = gpa,
> + .size = size,
> + .flags = 0,
> + };
> +
> + /*
> + * KVM_SET_MEMORY_ATTRIBUTES overwrites _all_ attributes. These flows
> + * need significant enhancements to support multiple attributes.
> + */
> + TEST_ASSERT(!attributes || attributes == KVM_MEMORY_ATTRIBUTE_PRIVATE,
> + "Update me to support multiple attributes!");
> +
> + vm_ioctl(vm, KVM_SET_MEMORY_ATTRIBUTES, &attr);
> +}
> +
> +
> +static inline void vm_mem_set_private(struct kvm_vm *vm, uint64_t gpa,
> + uint64_t size)
> +{
> + vm_set_memory_attributes(vm, gpa, size, KVM_MEMORY_ATTRIBUTE_PRIVATE);
> +}
> +
> +static inline void vm_mem_set_shared(struct kvm_vm *vm, uint64_t gpa,
> + uint64_t size)
> +{
> + vm_set_memory_attributes(vm, gpa, size, 0);
> +}
> +
> +void vm_guest_mem_fallocate(struct kvm_vm *vm, uint64_t gpa, uint64_t size,
> + bool punch_hole);
> +
> +static inline void vm_guest_mem_punch_hole(struct kvm_vm *vm, uint64_t gpa,
> + uint64_t size)
> +{
> + vm_guest_mem_fallocate(vm, gpa, size, true);
> +}
> +
> +static inline void vm_guest_mem_allocate(struct kvm_vm *vm, uint64_t gpa,
> + uint64_t size)
> +{
> + vm_guest_mem_fallocate(vm, gpa, size, false);
> +}
> +
> void vm_enable_dirty_ring(struct kvm_vm *vm, uint32_t ring_size);
> const char *vm_guest_mode_string(uint32_t i);
>
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index b63500fca627..95a553400ea9 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -1167,6 +1167,34 @@ void vm_mem_region_delete(struct kvm_vm *vm, uint32_t slot)
> __vm_mem_region_delete(vm, memslot2region(vm, slot), true);
> }
>
> +void vm_guest_mem_fallocate(struct kvm_vm *vm, uint64_t base, uint64_t size,
> + bool punch_hole)
> +{
> + const int mode = FALLOC_FL_KEEP_SIZE | (punch_hole ? FALLOC_FL_PUNCH_HOLE : 0);
> + struct userspace_mem_region *region;
> + uint64_t end = base + size;
> + uint64_t gpa, len;
> + off_t fd_offset;
> + int ret;
> +
> + for (gpa = base; gpa < end; gpa += len) {
> + uint64_t offset;
> +
> + region = userspace_mem_region_find(vm, gpa, gpa);
> + TEST_ASSERT(region && region->region.flags & KVM_MEM_GUEST_MEMFD,
> + "Private memory region not found for GPA 0x%lx", gpa);
> +
> + offset = (gpa - region->region.guest_phys_addr);
nit: why the parentheses?
> + fd_offset = region->region.guest_memfd_offset + offset;
> + len = min_t(uint64_t, end - gpa, region->region.memory_size - offset);
> +
> + ret = fallocate(region->region.guest_memfd, mode, fd_offset, len);
> + TEST_ASSERT(!ret, "fallocate() failed to %s at %lx (len = %lu), fd = %d, mode = %x, offset = %lx\n",
> + punch_hole ? "punch hole" : "allocate", gpa, len,
> + region->region.guest_memfd, mode, fd_offset);
> + }
> +}
> +
> /* Returns the size of a vCPU's kvm_run structure. */
> static int vcpu_mmap_sz(void)
> {
Nits aside:
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Cheers,
/fuad
> --
> 2.39.1
>
>