[PATCH 1/2] x86/virt/tdx: Use PFN directly for mapping guest private memory

Yan Zhao
2026-03-19T01:36:31Z

From: Sean Christopherson <seanjc@google.com>

Remove the completely unnecessary assumption that memory mapped into a TDX
guest is backed by refcounted struct page memory. From KVM's point of view,
TDH_MEM_PAGE_ADD and TDH_MEM_PAGE_AUG are glorified writes to PTEs, so they
have no business placing requirements on how KVM and guest_memfd manage
memory.

Rip out the misguided struct page assumptions/constraints and instead have
the two SEAMCALL wrapper APIs take PFN directly. This ensures that for
future huge page support in S-EPT, the kernel doesn't pick up even worse
assumptions like "a hugepage must be contained in a single folio".

Use "kvm_pfn_t pfn" for type safety. Using this KVM type is appropriate
since APIs tdh_mem_page_add() and tdh_mem_page_aug() are exported to KVM
only.

[ Yan: Replace "u64 pfn" with "kvm_pfn_t pfn" ]

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
---
arch/x86/include/asm/tdx.h | 5 +++--
arch/x86/kvm/vmx/tdx.c | 7 +++----
arch/x86/virt/vmx/tdx/tdx.c | 20 +++++++++++++-------
3 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index a149740b24e8..f3f0b1872176 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -6,6 +6,7 @@
#include <linux/init.h>
#include <linux/bits.h>
#include <linux/mmzone.h>
+#include <linux/kvm_types.h>

#include <asm/errno.h>
#include <asm/ptrace.h>
@@ -195,10 +196,10 @@ static inline int pg_level_to_tdx_sept_level(enum pg_level level)

u64 tdh_vp_enter(struct tdx_vp *vp, struct tdx_module_args *args);
u64 tdh_mng_addcx(struct tdx_td *td, struct page *tdcs_page);
-u64 tdh_mem_page_add(struct tdx_td *td, u64 gpa, struct page *page, struct page *source, u64 *ext_err1, u64 *ext_err2);
+u64 tdh_mem_page_add(struct tdx_td *td, u64 gpa, kvm_pfn_t pfn, struct page *source, u64 *ext_err1, u64 *ext_err2);
u64 tdh_mem_sept_add(struct tdx_td *td, u64 gpa, int level, struct page *page, u64 *ext_err1, u64 *ext_err2);
u64 tdh_vp_addcx(struct tdx_vp *vp, struct page *tdcx_page);
-u64 tdh_mem_page_aug(struct tdx_td *td, u64 gpa, int level, struct page *page, u64 *ext_err1, u64 *ext_err2);
+u64 tdh_mem_page_aug(struct tdx_td *td, u64 gpa, int level, kvm_pfn_t pfn, u64 *ext_err1, u64 *ext_err2);
u64 tdh_mem_range_block(struct tdx_td *td, u64 gpa, int level, u64 *ext_err1, u64 *ext_err2);
u64 tdh_mng_key_config(struct tdx_td *td);
u64 tdh_mng_create(struct tdx_td *td, u16 hkid);
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 1e47c194af53..1f1abc5b5655 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1624,8 +1624,8 @@ static int tdx_mem_page_add(struct kvm *kvm, gfn_t gfn, enum pg_level level,
KVM_BUG_ON(!kvm_tdx->page_add_src, kvm))
return -EIO;

- err = tdh_mem_page_add(&kvm_tdx->td, gpa, pfn_to_page(pfn),
- kvm_tdx->page_add_src, &entry, &level_state);
+ err = tdh_mem_page_add(&kvm_tdx->td, gpa, pfn, kvm_tdx->page_add_src,
+ &entry, &level_state);
if (unlikely(tdx_operand_busy(err)))
return -EBUSY;

@@ -1640,12 +1640,11 @@ static int tdx_mem_page_aug(struct kvm *kvm, gfn_t gfn,
{
int tdx_level = pg_level_to_tdx_sept_level(level);
struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
- struct page *page = pfn_to_page(pfn);
gpa_t gpa = gfn_to_gpa(gfn);
u64 entry, level_state;
u64 err;

- err = tdh_mem_page_aug(&kvm_tdx->td, gpa, tdx_level, page, &entry, &level_state);
+ err = tdh_mem_page_aug(&kvm_tdx->td, gpa, tdx_level, pfn, &entry, &level_state);
if (unlikely(tdx_operand_busy(err)))
return -EBUSY;

diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index cb9b3210ab71..a9dd75190c67 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -30,7 +30,6 @@
#include <linux/suspend.h>
#include <linux/syscore_ops.h>
#include <linux/idr.h>
-#include <linux/kvm_types.h>
#include <asm/page.h>
#include <asm/special_insns.h>
#include <asm/msr-index.h>
@@ -1568,6 +1567,11 @@ static void tdx_clflush_page(struct page *page)
clflush_cache_range(page_to_virt(page), PAGE_SIZE);
}

+static void tdx_clflush_pfn(kvm_pfn_t pfn)
+{
+ clflush_cache_range(__va(PFN_PHYS(pfn)), PAGE_SIZE);
+}
+
noinstr u64 tdh_vp_enter(struct tdx_vp *td, struct tdx_module_args *args)
{
args->rcx = td->tdvpr_pa;
@@ -1588,17 +1592,18 @@ u64 tdh_mng_addcx(struct tdx_td *td, struct page *tdcs_page)
}
EXPORT_SYMBOL_FOR_KVM(tdh_mng_addcx);

-u64 tdh_mem_page_add(struct tdx_td *td, u64 gpa, struct page *page, struct page *source, u64 *ext_err1, u64 *ext_err2)
+u64 tdh_mem_page_add(struct tdx_td *td, u64 gpa, kvm_pfn_t pfn, struct page *source,
+ u64 *ext_err1, u64 *ext_err2)
{
struct tdx_module_args args = {
.rcx = gpa,
.rdx = tdx_tdr_pa(td),
- .r8 = page_to_phys(page),
+ .r8 = PFN_PHYS(pfn),
.r9 = page_to_phys(source),
};
u64 ret;

- tdx_clflush_page(page);
+ tdx_clflush_pfn(pfn);
ret = seamcall_ret(TDH_MEM_PAGE_ADD, &args);

*ext_err1 = args.rcx;
@@ -1639,16 +1644,17 @@ u64 tdh_vp_addcx(struct tdx_vp *vp, struct page *tdcx_page)
}
EXPORT_SYMBOL_FOR_KVM(tdh_vp_addcx);

-u64 tdh_mem_page_aug(struct tdx_td *td, u64 gpa, int level, struct page *page, u64 *ext_err1, u64 *ext_err2)
+u64 tdh_mem_page_aug(struct tdx_td *td, u64 gpa, int level, kvm_pfn_t pfn,
+ u64 *ext_err1, u64 *ext_err2)
{
struct tdx_module_args args = {
.rcx = gpa | level,
.rdx = tdx_tdr_pa(td),
- .r8 = page_to_phys(page),
+ .r8 = PFN_PHYS(pfn),
};
u64 ret;

- tdx_clflush_page(page);
+ tdx_clflush_pfn(pfn);
ret = seamcall_ret(TDH_MEM_PAGE_AUG, &args);

*ext_err1 = args.rcx;
--
2.43.2