[PATCH v8 23/46] KVM: TDX: Make source page optional for KVM_TDX_INIT_MEM_REGION
From: Ackerley Tng via B4 Relay <devnull+ackerleytng.google.com@kernel.org>
Date: 2026-06-19 00:31:49
Also in:
b4-sent, kvm, linux-doc, linux-kselftest, linux-mm, linux-trace-kernel, lkml
Subsystem:
documentation, kernel virtual machine (kvm), kernel virtual machine for x86 (kvm/x86), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Jonathan Corbet, Paolo Bonzini, Sean Christopherson, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: Ackerley Tng <redacted> Update tdx_gmem_post_populate() to handle cases where a source page is not explicitly provided. Instead of returning -EOPNOTSUPP when src_page is NULL, default to using the page associated with the destination PFN. This change allows for in-place memory conversion where the data is already present in the target PFN, ensuring the TDX module has a valid source page reference for the TDH.MEM.PAGE.ADD operation. Signed-off-by: Ackerley Tng <redacted> Signed-off-by: Sean Christopherson <seanjc@google.com> --- Documentation/virt/kvm/x86/intel-tdx.rst | 4 ++++ arch/x86/kvm/vmx/tdx.c | 11 ++++++++--- 2 files changed, 12 insertions(+), 3 deletions(-)
diff --git a/Documentation/virt/kvm/x86/intel-tdx.rst b/Documentation/virt/kvm/x86/intel-tdx.rst
index 6a222e9d09541..74357fe87f9ec 100644
--- a/Documentation/virt/kvm/x86/intel-tdx.rst
+++ b/Documentation/virt/kvm/x86/intel-tdx.rst@@ -158,6 +158,10 @@ KVM_TDX_INIT_MEM_REGION Initialize @nr_pages TDX guest private memory starting from @gpa with userspace provided data from @source_addr. @source_addr must be PAGE_SIZE-aligned. +If guest_memfd in-place conversion is enabled, pass NULL for @source_addr to +initialize the memory region using memory contents already populated in +guest_memfd memory. + Note, before calling this sub command, memory attribute of the range [gpa, gpa + nr_pages] needs to be private. Userspace can use KVM_SET_MEMORY_ATTRIBUTES to set the attribute.
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index ffe9d0db58c59..56d10333c61a7 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c@@ -3198,8 +3198,12 @@ static int tdx_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, if (KVM_BUG_ON(kvm_tdx->page_add_src, kvm)) return -EIO; - if (!src_page) - return -EOPNOTSUPP; + if (!src_page) { + if (!gmem_in_place_conversion) + return -EOPNOTSUPP; + + src_page = pfn_to_page(pfn); + } kvm_tdx->page_add_src = src_page; ret = kvm_tdp_mmu_map_private_pfn(arg->vcpu, gfn, pfn);
@@ -3278,7 +3282,8 @@ static int tdx_vcpu_init_mem_region(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *c break; } - region.source_addr += PAGE_SIZE; + if (region.source_addr) + region.source_addr += PAGE_SIZE; region.gpa += PAGE_SIZE; region.nr_pages--;
--
2.55.0.rc0.738.g0c8ab3ebcc-goog