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Message-ID: <aK6BBc/qrfxJKUUf@yzhao56-desk.sh.intel.com>
Date: Wed, 27 Aug 2025 11:52:37 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: Binbin Wu <binbin.wu@...ux.intel.com>, Sagi Shahar <sagis@...gle.com>,
<linux-kselftest@...r.kernel.org>, Paolo Bonzini <pbonzini@...hat.com>,
"Shuah Khan" <shuah@...nel.org>, Sean Christopherson <seanjc@...gle.com>,
"Ackerley Tng" <ackerleytng@...gle.com>, Ryan Afranji <afranji@...gle.com>,
Andrew Jones <ajones@...tanamicro.com>, Isaku Yamahata
<isaku.yamahata@...el.com>, "Erdem Aktas" <erdemaktas@...gle.com>, Rick
Edgecombe <rick.p.edgecombe@...el.com>, Roger Wang <runanwang@...gle.com>,
Oliver Upton <oliver.upton@...ux.dev>, "Pratik R. Sampat"
<pratikrajesh.sampat@....com>, Reinette Chatre <reinette.chatre@...el.com>,
Ira Weiny <ira.weiny@...el.com>, Chao Gao <chao.gao@...el.com>, Chenyi Qiang
<chenyi.qiang@...el.com>, <linux-kernel@...r.kernel.org>,
<kvm@...r.kernel.org>
Subject: Re: [PATCH v9 14/19] KVM: selftests: Add helpers to init TDX memory
and finalize VM
On Wed, Aug 27, 2025 at 10:44:58AM +0800, Yan Zhao wrote:
> On Wed, Aug 27, 2025 at 10:24:03AM +0800, Binbin Wu wrote:
> >
> >
> > On 8/26/2025 9:07 AM, Yan Zhao wrote:
> > > On Mon, Aug 25, 2025 at 02:02:00PM -0500, Sagi Shahar wrote:
> > > > On Mon, Aug 25, 2025 at 3:41 AM Yan Zhao <yan.y.zhao@...el.com> wrote:
> > > > > On Wed, Aug 20, 2025 at 09:29:07PM -0700, Sagi Shahar wrote:
> > > > > > From: Ackerley Tng <ackerleytng@...gle.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@...gle.com>
> > > > > > Co-developed-by: Erdem Aktas <erdemaktas@...gle.com>
> > > > > > Signed-off-by: Erdem Aktas <erdemaktas@...gle.com>
> > > > > > Co-developed-by: Sagi Shahar <sagis@...gle.com>
> > > > > > Signed-off-by: Sagi Shahar <sagis@...gle.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.
> > > From the implementation of tdx_init_pages(), it also invokes
> > > tdx_init_mem_region(), which further invokes ioctl KVM_TDX_INIT_MEM_REGION.
> > >
> > > However, if the region is with guest_memfd == -1, the ioctl
> > > KVM_TDX_INIT_MEM_REGION should fail as kvm_gmem_populate() won't succeed.
> > >
> > > So, I'm wondering why there's a need to for the case of
> > > "region->region.guest_memfd == -1".
> > >
> > > Or anything I missed?
> > I had the same question in v8
> > https://lore.kernel.org/lkml/4b7e7099-79da-4178-8f16-6780d8137ae1@linux.intel.com/
> I agree with you.
> In patch "KVM: selftests: TDX: Test LOG_DIRTY_PAGES flag to a non-GUEST_MEMFD
> memslot", virt_map_shared() prevents the non-guest_memfd region from being
> searched by the load_td_private_memory().
Specifically, there's no __vm_phy_pages_alloc() being invoked with protected
being true for the non-guest-memfd region in
verify_log_dirty_pages_flag_on_non_gmemfd_slot().
> Otherwise, the tdx_init_mem_region() would fail on this region.
>
> > I guess the code path for non-guest_memfd is due to some old versions of TDX KVM
> > code before upstream. Currently, KVM doesn't support private memory from
> > non-guest_memfd backed memory.
> I guess so. Maybe just drop this case and assert?
>
> TEST_ASSERT(region->region.guest_memfd != -1, "TDX private memory only supports
> guest_memfd backend\n");
>
> > >
> > > > > > + 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
> > > > > >
> > > > > >
> >
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