Re: [PATCH v9 14/19] KVM: selftests: Add helpers to init TDX memory and finalize VM

[Sagi Shahar <sagis@google.com>]

On Mon, Aug 25, 2025 at 3:41 AM Yan Zhao <yan.y.zhao@intel.com> wrote:
>
> On Wed, Aug 20, 2025 at 09:29:07PM -0700, Sagi Shahar wrote:
> > From: Ackerley Tng <ackerleytng@google.com>
> >
> > TDX protected memory needs to be measured and encrypted before it can be
> > used by the guest. Traverse the VM's memory regions and initialize all
> > the protected ranges by calling KVM_TDX_INIT_MEM_REGION.
> >
> > Once all the memory is initialized, the VM can be finalized by calling
> > KVM_TDX_FINALIZE_VM.
> >
> > Signed-off-by: Ackerley Tng <ackerleytng@google.com>
> > Co-developed-by: Erdem Aktas <erdemaktas@google.com>
> > Signed-off-by: Erdem Aktas <erdemaktas@google.com>
> > Co-developed-by: Sagi Shahar <sagis@google.com>
> > Signed-off-by: Sagi Shahar <sagis@google.com>
> > ---
> >  .../selftests/kvm/include/x86/tdx/tdx_util.h  |  2 +
> >  .../selftests/kvm/lib/x86/tdx/tdx_util.c      | 97 +++++++++++++++++++
> >  2 files changed, 99 insertions(+)
> >
> > diff --git a/tools/testing/selftests/kvm/include/x86/tdx/tdx_util.h b/tools/testing/selftests/kvm/include/x86/tdx/tdx_util.h
> > index a2509959c7ce..2467b6c35557 100644
> > --- a/tools/testing/selftests/kvm/include/x86/tdx/tdx_util.h
> > +++ b/tools/testing/selftests/kvm/include/x86/tdx/tdx_util.h
> > @@ -71,4 +71,6 @@ void vm_tdx_load_common_boot_parameters(struct kvm_vm *vm);
> >  void vm_tdx_load_vcpu_boot_parameters(struct kvm_vm *vm, struct kvm_vcpu *vcpu);
> >  void vm_tdx_set_vcpu_entry_point(struct kvm_vcpu *vcpu, void *guest_code);
> >
> > +void vm_tdx_finalize(struct kvm_vm *vm);
> > +
> >  #endif // SELFTESTS_TDX_TDX_UTIL_H
> > diff --git a/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c b/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
> > index d8eab99d9333..4024587ed3c2 100644
> > --- a/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
> > +++ b/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
> > @@ -274,3 +274,100 @@ void vm_tdx_init_vm(struct kvm_vm *vm, uint64_t attributes)
> >
> >       free(init_vm);
> >  }
> > +
> > +static void tdx_init_mem_region(struct kvm_vm *vm, void *source_pages,
> > +                             uint64_t gpa, uint64_t size)
> > +{
> > +     uint32_t metadata = KVM_TDX_MEASURE_MEMORY_REGION;
> > +     struct kvm_tdx_init_mem_region mem_region = {
> > +             .source_addr = (uint64_t)source_pages,
> > +             .gpa = gpa,
> > +             .nr_pages = size / PAGE_SIZE,
> > +     };
> > +     struct kvm_vcpu *vcpu;
> > +
> > +     vcpu = list_first_entry_or_null(&vm->vcpus, struct kvm_vcpu, list);
> > +
> > +     TEST_ASSERT((mem_region.nr_pages > 0) &&
> > +                 ((mem_region.nr_pages * PAGE_SIZE) == size),
> > +                 "Cannot add partial pages to the guest memory.\n");
> > +     TEST_ASSERT(((uint64_t)source_pages & (PAGE_SIZE - 1)) == 0,
> > +                 "Source memory buffer is not page aligned\n");
> > +     vm_tdx_vcpu_ioctl(vcpu, KVM_TDX_INIT_MEM_REGION, metadata, &mem_region);
> > +}
> > +
> > +static void tdx_init_pages(struct kvm_vm *vm, void *hva, uint64_t gpa,
> > +                        uint64_t size)
> > +{
> > +     void *scratch_page = calloc(1, PAGE_SIZE);
> > +     uint64_t nr_pages = size / PAGE_SIZE;
> > +     int i;
> > +
> > +     TEST_ASSERT(scratch_page,
> > +                 "Could not allocate memory for loading memory region");
> > +
> > +     for (i = 0; i < nr_pages; i++) {
> > +             memcpy(scratch_page, hva, PAGE_SIZE);
> > +
> > +             tdx_init_mem_region(vm, scratch_page, gpa, PAGE_SIZE);
> > +
> > +             hva += PAGE_SIZE;
> > +             gpa += PAGE_SIZE;
> > +     }
> > +
> > +     free(scratch_page);
> > +}
> > +
> > +static void load_td_private_memory(struct kvm_vm *vm)
> > +{
> > +     struct userspace_mem_region *region;
> > +     int ctr;
> > +
> > +     hash_for_each(vm->regions.slot_hash, ctr, region, slot_node) {
> > +             const struct sparsebit *protected_pages = region->protected_phy_pages;
> > +             const vm_paddr_t gpa_base = region->region.guest_phys_addr;
> > +             const uint64_t hva_base = region->region.userspace_addr;
> > +             const sparsebit_idx_t lowest_page_in_region = gpa_base >> vm->page_shift;
> > +
> > +             sparsebit_idx_t i;
> > +             sparsebit_idx_t j;
> > +
> > +             if (!sparsebit_any_set(protected_pages))
> > +                     continue;
> > +
> > +             sparsebit_for_each_set_range(protected_pages, i, j) {
> > +                     const uint64_t size_to_load = (j - i + 1) * vm->page_size;
> > +                     const uint64_t offset =
> > +                             (i - lowest_page_in_region) * vm->page_size;
> > +                     const uint64_t hva = hva_base + offset;
> > +                     const uint64_t gpa = gpa_base + offset;
> > +
> > +                     vm_set_memory_attributes(vm, gpa, size_to_load,
> > +                                              KVM_MEMORY_ATTRIBUTE_PRIVATE);
> > +
> > +                     /*
> > +                      * Here, memory is being loaded from hva to gpa. If the memory
> > +                      * mapped to hva is also used to back gpa, then a copy has to be
> > +                      * made just for loading, since KVM_TDX_INIT_MEM_REGION ioctl
> > +                      * cannot encrypt memory in place.
> > +                      *
> > +                      * To determine if memory mapped to hva is also used to back
> > +                      * gpa, use a heuristic:
> > +                      *
> > +                      * If this memslot has guest_memfd, then this memslot should
> > +                      * have memory backed from two sources: hva for shared memory
> > +                      * and gpa will be backed by guest_memfd.
> > +                      */
> > +                     if (region->region.guest_memfd == -1)
> Why to pass !guest_memfd region to tdx_init_mem_region()?
>

Not sure I understand your comment.

>
> > +                             tdx_init_pages(vm, (void *)hva, gpa, size_to_load);
> > +                     else
> > +                             tdx_init_mem_region(vm, (void *)hva, gpa, size_to_load);
> > +             }
> > +     }
> > +}
> > +
> > +void vm_tdx_finalize(struct kvm_vm *vm)
> > +{
> > +     load_td_private_memory(vm);
> > +     vm_tdx_vm_ioctl(vm, KVM_TDX_FINALIZE_VM, 0, NULL);
> > +}
> > --
> > 2.51.0.rc1.193.gad69d77794-goog
> >
> >