[PATCH v2 00/11] Unify TDCALL/SEAMCALL and TDVMCALL assembly

[PATCH v2 00/11] Unify TDCALL/SEAMCALL and TDVMCALL assembly

[Kai Huang]

Hi Peter, Kirill, all,

This series unifies the assembly code for TDCALL/SEAMCALL and TDVMCALL.
Now all of them use one singe TDX_MODULE_CALL asm macro.

With this series, I have verified the TDX guest can boot successfully
and the TDX module can also be initialized successfully.

The last two patches are SEAMCALL patches that are needed for TDX host
patchset.  They are not mandatory to be here though, i.e., can be in the
TDX host support series.  I put them here so we can have a complete view
how TDCALL/SEAMCALL and TDVMCALL are implemented.

Could you help to review?  Thanks in advance.

(Removed KVM list -- Sean/Paolo/Isaku are still CC'ed.)

------- Histroy --------

v1 -> v2:
 - Rebased to 6.5-rc2.
 - Fixed comments from Peter and others.
 - Split patch "x86/tdx: Unify TDX_HYPERCALL and TDX_MODULE_CALL assembly"
   into three smaller patches for better review.
 - A new patch to skip saving output registers when SEAMCALL fails due to
   VMFailInvalid.  
 - Removed patch "x86/tdx: Use cmovc to save a label in TDX_MODULE_CALL asm"
 - Merged patch "x86/tdx: Move FRAME_BEGIN/END to TDX_MODULE_CALL asm macro"
   to the new patch mentioned above.

v1: https://lore.kernel.org/lkml/b95c4169-88c8-219e-87b7-6c4e058c246a@suse.com/T/


Kai Huang (11):
  x86/tdx: Zero out the missing RSI in TDX_HYPERCALL macro
  x86/tdx: Skip saving output regs when SEAMCALL fails with
    VMFailInvalid
  x86/tdx: Make macros of TDCALLs consistent with the spec
  x86/tdx: Rename __tdx_module_call() to __tdcall()
  x86/tdx: Pass TDCALL/SEAMCALL input/output registers via a structure
  x86/tdx: Extend TDX_MODULE_CALL to support more TDCALL/SEAMCALL leafs
  x86/tdx: Make TDX_HYPERCALL asm similar to TDX_MODULE_CALL
  x86/tdx: Reimplement __tdx_hypercall() using TDX_MODULE_CALL asm
  x86/tdx: Remove 'struct tdx_hypercall_args'
  x86/virt/tdx: Wire up basic SEAMCALL functions
  x86/virt/tdx: Allow SEAMCALL to handle #UD and #GP

 arch/x86/Kconfig                  |  12 ++
 arch/x86/Makefile                 |   2 +
 arch/x86/boot/compressed/tdx.c    |   6 +-
 arch/x86/coco/tdx/tdcall.S        | 231 ++++--------------------------
 arch/x86/coco/tdx/tdx-shared.c    |  28 +++-
 arch/x86/coco/tdx/tdx.c           |  73 +++++-----
 arch/x86/include/asm/shared/tdx.h |  83 ++++++-----
 arch/x86/include/asm/tdx.h        |  10 ++
 arch/x86/kernel/asm-offsets.c     |  33 ++---
 arch/x86/virt/Makefile            |   2 +
 arch/x86/virt/vmx/Makefile        |   2 +
 arch/x86/virt/vmx/tdx/Makefile    |   2 +
 arch/x86/virt/vmx/tdx/seamcall.S  |  42 ++++++
 arch/x86/virt/vmx/tdx/tdxcall.S   | 227 ++++++++++++++++++++++-------
 14 files changed, 406 insertions(+), 347 deletions(-)
 create mode 100644 arch/x86/virt/Makefile
 create mode 100644 arch/x86/virt/vmx/Makefile
 create mode 100644 arch/x86/virt/vmx/tdx/Makefile
 create mode 100644 arch/x86/virt/vmx/tdx/seamcall.S


base-commit: fdf0eaf11452d72945af31804e2a1048ee1b574c
-- 
2.41.0

[PATCH v2 01/11] x86/tdx: Zero out the missing RSI in TDX_HYPERCALL macro

[Kai Huang]

In the TDX_HYPERCALL asm, after the TDCALL instruction returns from the
untrusted VMM, the registers that the TDX guest shares to the VMM need
to be cleared to avoid speculative execution of VMM-provided values.

RSI is specified in the bitmap of those registers, but it is missing
when zeroing out those registers in the current TDX_HYPERCALL.

It was there when it was originally added in commit 752d13305c78
("x86/tdx: Expand __tdx_hypercall() to handle more arguments"), but was
later removed in commit 1e70c680375a ("x86/tdx: Do not corrupt
frame-pointer in __tdx_hypercall()"), which was correct because %rsi is
later restored in the "pop %rsi".  However a later commit 7a3a401874be
("x86/tdx: Drop flags from __tdx_hypercall()") removed that "pop %rsi"
but forgot to add the "xor %rsi, %rsi" back.

Fix by adding it back.

Fixes: 7a3a401874be ("x86/tdx: Drop flags from __tdx_hypercall()")
Signed-off-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---
 arch/x86/coco/tdx/tdcall.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/coco/tdx/tdcall.S b/arch/x86/coco/tdx/tdcall.S
index b193c0a1d8db..2eca5f43734f 100644
--- a/arch/x86/coco/tdx/tdcall.S
+++ b/arch/x86/coco/tdx/tdcall.S
@@ -195,6 +195,7 @@ SYM_FUNC_END(__tdx_module_call)
 	xor %r10d, %r10d
 	xor %r11d, %r11d
 	xor %rdi,  %rdi
+	xor %rsi,  %rsi
 	xor %rdx,  %rdx
 
 	/* Restore callee-saved GPRs as mandated by the x86_64 ABI */
-- 
2.41.0

[PATCH v2 02/11] x86/tdx: Skip saving output regs when SEAMCALL fails with VMFailInvalid

[Kai Huang]

If SEAMCALL fails with VMFailInvalid, the SEAM software (e.g., the TDX
module) won't have chance to set any output register.  Skip saving the
output registers to the structure in this case.

Also, as '.Lno_output_struct' is the very last symbol before RET, rename
it to '.Lout' to make it short.

Opportunistically make the asm directives unindented.

Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kai Huang <kai.huang@intel.com>
---

v1 -> v2:
 - A new patch to improve SEAMCALL VMFailInvalid failure, with v1 patch
   "x86/tdx: Move FRAME_BEGIN/END to TDX_MODULE_CALL asm macro" merged.

---
 arch/x86/coco/tdx/tdcall.S      |  3 ---
 arch/x86/virt/vmx/tdx/tdxcall.S | 29 ++++++++++++++++++++---------
 2 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/arch/x86/coco/tdx/tdcall.S b/arch/x86/coco/tdx/tdcall.S
index 2eca5f43734f..e5d4b7d8ecd4 100644
--- a/arch/x86/coco/tdx/tdcall.S
+++ b/arch/x86/coco/tdx/tdcall.S
@@ -78,10 +78,7 @@
  * Return status of TDCALL via RAX.
  */
 SYM_FUNC_START(__tdx_module_call)
-	FRAME_BEGIN
 	TDX_MODULE_CALL host=0
-	FRAME_END
-	RET
 SYM_FUNC_END(__tdx_module_call)
 
 /*
diff --git a/arch/x86/virt/vmx/tdx/tdxcall.S b/arch/x86/virt/vmx/tdx/tdxcall.S
index 49a54356ae99..6bdf6e137953 100644
--- a/arch/x86/virt/vmx/tdx/tdxcall.S
+++ b/arch/x86/virt/vmx/tdx/tdxcall.S
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 #include <asm/asm-offsets.h>
+#include <asm/frame.h>
 #include <asm/tdx.h>
 
 /*
@@ -18,6 +19,7 @@
  *            TDX module.
  */
 .macro TDX_MODULE_CALL host:req
+	FRAME_BEGIN
 	/*
 	 * R12 will be used as temporary storage for struct tdx_module_output
 	 * pointer. Since R12-R15 registers are not used by TDCALL/SEAMCALL
@@ -44,7 +46,7 @@
 	mov %rsi, %rcx
 	/* Leave input param 2 in RDX */
 
-	.if \host
+.if \host
 	seamcall
 	/*
 	 * SEAMCALL instruction is essentially a VMExit from VMX root
@@ -57,13 +59,10 @@
 	 * This value will never be used as actual SEAMCALL error code as
 	 * it is from the Reserved status code class.
 	 */
-	jnc .Lno_vmfailinvalid
-	mov $TDX_SEAMCALL_VMFAILINVALID, %rax
-.Lno_vmfailinvalid:
-
-	.else
+	jc .Lseamcall_vmfailinvalid
+.else
 	tdcall
-	.endif
+.endif
 
 	/*
 	 * Fetch output pointer from stack to R12 (It is used
@@ -80,7 +79,7 @@
 	 * Other registers may contain details of the failure.
 	 */
 	test %r12, %r12
-	jz .Lno_output_struct
+	jz .Lout
 
 	/* Copy result registers to output struct: */
 	movq %rcx, TDX_MODULE_rcx(%r12)
@@ -90,7 +89,19 @@
 	movq %r10, TDX_MODULE_r10(%r12)
 	movq %r11, TDX_MODULE_r11(%r12)
 
-.Lno_output_struct:
+.Lout:
 	/* Restore the state of R12 register */
 	pop %r12
+
+	FRAME_END
+	RET
+
+.if \host
+.Lseamcall_vmfailinvalid:
+	mov $TDX_SEAMCALL_VMFAILINVALID, %rax
+	/* pop the unused output pointer back to %r9 */
+	pop %r9
+	jmp .Lout
+.endif	/* \host */
+
 .endm
-- 
2.41.0

[PATCH v2 03/11] x86/tdx: Make macros of TDCALLs consistent with the spec

[Kai Huang]

The TDX spec names all TDCALLs with prefix "TDG".  Currently, the kernel
doesn't follow such convention for the macros of those TDCALLs but uses
prefix "TDX_" for all of them.  Although it's arguable whether the TDX
spec names those TDCALLs properly, it's better for the kernel to follow
the spec when naming those macros.

Change all macros of TDCALLs to make them consistent with the spec.  As
a bonus, they get distinguished easily from the host-side SEAMCALLs,
which all have prefix "TDH".

No functional change intended.

Signed-off-by: Kai Huang <kai.huang@intel.com>
---

v1 -> v2:
 - Rebase to 6.5-rc2.

---
 arch/x86/coco/tdx/tdx-shared.c    |  4 ++--
 arch/x86/coco/tdx/tdx.c           |  8 ++++----
 arch/x86/include/asm/shared/tdx.h | 10 +++++-----
 3 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx-shared.c b/arch/x86/coco/tdx/tdx-shared.c
index ef20ddc37b58..f10cd3e4a04e 100644
--- a/arch/x86/coco/tdx/tdx-shared.c
+++ b/arch/x86/coco/tdx/tdx-shared.c
@@ -35,7 +35,7 @@ static unsigned long try_accept_one(phys_addr_t start, unsigned long len,
 	}
 
 	tdcall_rcx = start | page_size;
-	if (__tdx_module_call(TDX_ACCEPT_PAGE, tdcall_rcx, 0, 0, 0, NULL))
+	if (__tdx_module_call(TDG_MEM_PAGE_ACCEPT, tdcall_rcx, 0, 0, 0, NULL))
 		return 0;
 
 	return accept_size;
@@ -45,7 +45,7 @@ bool tdx_accept_memory(phys_addr_t start, phys_addr_t end)
 {
 	/*
 	 * For shared->private conversion, accept the page using
-	 * TDX_ACCEPT_PAGE TDX module call.
+	 * TDG_MEM_PAGE_ACCEPT TDX module call.
 	 */
 	while (start < end) {
 		unsigned long len = end - start;
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 1d6b863c42b0..05785df66b1c 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -91,7 +91,7 @@ int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport)
 {
 	u64 ret;
 
-	ret = __tdx_module_call(TDX_GET_REPORT, virt_to_phys(tdreport),
+	ret = __tdx_module_call(TDG_MR_REPORT, virt_to_phys(tdreport),
 				virt_to_phys(reportdata), TDREPORT_SUBTYPE_0,
 				0, NULL);
 	if (ret) {
@@ -152,7 +152,7 @@ static void tdx_parse_tdinfo(u64 *cc_mask)
 	 * Guest-Host-Communication Interface (GHCI), section 2.4.2 TDCALL
 	 * [TDG.VP.INFO].
 	 */
-	tdx_module_call(TDX_GET_INFO, 0, 0, 0, 0, &out);
+	tdx_module_call(TDG_VP_INFO, 0, 0, 0, 0, &out);
 
 	/*
 	 * The highest bit of a guest physical address is the "sharing" bit.
@@ -594,7 +594,7 @@ void tdx_get_ve_info(struct ve_info *ve)
 	 * Note, the TDX module treats virtual NMIs as inhibited if the #VE
 	 * valid flag is set. It means that NMI=>#VE will not result in a #DF.
 	 */
-	tdx_module_call(TDX_GET_VEINFO, 0, 0, 0, 0, &out);
+	tdx_module_call(TDG_VP_VEINFO_GET, 0, 0, 0, 0, &out);
 
 	/* Transfer the output parameters */
 	ve->exit_reason = out.rcx;
@@ -774,7 +774,7 @@ void __init tdx_early_init(void)
 	cc_set_mask(cc_mask);
 
 	/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
-	tdx_module_call(TDX_WR, 0, TDCS_NOTIFY_ENABLES, 0, -1ULL, NULL);
+	tdx_module_call(TDG_VM_WR, 0, TDCS_NOTIFY_ENABLES, 0, -1ULL, NULL);
 
 	/*
 	 * All bits above GPA width are reserved and kernel treats shared bit
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index 7513b3bb69b7..78f109446da6 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -11,11 +11,11 @@
 #define TDX_IDENT		"IntelTDX    "
 
 /* TDX module Call Leaf IDs */
-#define TDX_GET_INFO			1
-#define TDX_GET_VEINFO			3
-#define TDX_GET_REPORT			4
-#define TDX_ACCEPT_PAGE			6
-#define TDX_WR				8
+#define TDG_VP_INFO			1
+#define TDG_VP_VEINFO_GET		3
+#define TDG_MR_REPORT			4
+#define TDG_MEM_PAGE_ACCEPT		6
+#define TDG_VM_WR			8
 
 /* TDCS fields. To be used by TDG.VM.WR and TDG.VM.RD module calls */
 #define TDCS_NOTIFY_ENABLES		0x9100000000000010
-- 
2.41.0

[PATCH v2 04/11] x86/tdx: Rename __tdx_module_call() to __tdcall()

[Kai Huang]

__tdx_module_call() is only used by the TDX guest to issue TDCALL to the
TDX module.  Rename it to __tdcall() to match its behaviour, e.g., it
cannot be used to make host-side SEAMCALL.

Also rename tdx_module_call() which is a wrapper of __tdx_module_call()
to tdcall().

No functional change intended.

Signed-off-by: Kai Huang <kai.huang@intel.com>
---

v1 -> v2:
 - Rebase to 6.5-rc2.

---
 arch/x86/coco/tdx/tdcall.S        | 10 +++++-----
 arch/x86/coco/tdx/tdx-shared.c    |  2 +-
 arch/x86/coco/tdx/tdx.c           | 18 +++++++++---------
 arch/x86/include/asm/shared/tdx.h |  4 ++--
 4 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/arch/x86/coco/tdx/tdcall.S b/arch/x86/coco/tdx/tdcall.S
index e5d4b7d8ecd4..6aebac08f2bf 100644
--- a/arch/x86/coco/tdx/tdcall.S
+++ b/arch/x86/coco/tdx/tdcall.S
@@ -40,8 +40,8 @@
 .section .noinstr.text, "ax"
 
 /*
- * __tdx_module_call()  - Used by TDX guests to request services from
- * the TDX module (does not include VMM services) using TDCALL instruction.
+ * __tdcall()  - Used by TDX guests to request services from the TDX
+ * module (does not include VMM services) using TDCALL instruction.
  *
  * Transforms function call register arguments into the TDCALL register ABI.
  * After TDCALL operation, TDX module output is saved in @out (if it is
@@ -62,7 +62,7 @@
  *
  *-------------------------------------------------------------------------
  *
- * __tdx_module_call() function ABI:
+ * __tdcall() function ABI:
  *
  * @fn  (RDI)          - TDCALL Leaf ID,    moved to RAX
  * @rcx (RSI)          - Input parameter 1, moved to RCX
@@ -77,9 +77,9 @@
  *
  * Return status of TDCALL via RAX.
  */
-SYM_FUNC_START(__tdx_module_call)
+SYM_FUNC_START(__tdcall)
 	TDX_MODULE_CALL host=0
-SYM_FUNC_END(__tdx_module_call)
+SYM_FUNC_END(__tdcall)
 
 /*
  * TDX_HYPERCALL - Make hypercalls to a TDX VMM using TDVMCALL leaf of TDCALL
diff --git a/arch/x86/coco/tdx/tdx-shared.c b/arch/x86/coco/tdx/tdx-shared.c
index f10cd3e4a04e..90631abdac34 100644
--- a/arch/x86/coco/tdx/tdx-shared.c
+++ b/arch/x86/coco/tdx/tdx-shared.c
@@ -35,7 +35,7 @@ static unsigned long try_accept_one(phys_addr_t start, unsigned long len,
 	}
 
 	tdcall_rcx = start | page_size;
-	if (__tdx_module_call(TDG_MEM_PAGE_ACCEPT, tdcall_rcx, 0, 0, 0, NULL))
+	if (__tdcall(TDG_MEM_PAGE_ACCEPT, tdcall_rcx, 0, 0, 0, NULL))
 		return 0;
 
 	return accept_size;
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 05785df66b1c..8c13944925e3 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -66,10 +66,10 @@ EXPORT_SYMBOL_GPL(tdx_kvm_hypercall);
  * should only be used for calls that have no legitimate reason to fail
  * or where the kernel can not survive the call failing.
  */
-static inline void tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
-				   struct tdx_module_output *out)
+static inline void tdcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
+			  struct tdx_module_output *out)
 {
-	if (__tdx_module_call(fn, rcx, rdx, r8, r9, out))
+	if (__tdcall(fn, rcx, rdx, r8, r9, out))
 		panic("TDCALL %lld failed (Buggy TDX module!)\n", fn);
 }
 
@@ -91,9 +91,9 @@ int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport)
 {
 	u64 ret;
 
-	ret = __tdx_module_call(TDG_MR_REPORT, virt_to_phys(tdreport),
-				virt_to_phys(reportdata), TDREPORT_SUBTYPE_0,
-				0, NULL);
+	ret = __tdcall(TDG_MR_REPORT, virt_to_phys(tdreport),
+			virt_to_phys(reportdata), TDREPORT_SUBTYPE_0,
+			0, NULL);
 	if (ret) {
 		if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
 			return -EINVAL;
@@ -152,7 +152,7 @@ static void tdx_parse_tdinfo(u64 *cc_mask)
 	 * Guest-Host-Communication Interface (GHCI), section 2.4.2 TDCALL
 	 * [TDG.VP.INFO].
 	 */
-	tdx_module_call(TDG_VP_INFO, 0, 0, 0, 0, &out);
+	tdcall(TDG_VP_INFO, 0, 0, 0, 0, &out);
 
 	/*
 	 * The highest bit of a guest physical address is the "sharing" bit.
@@ -594,7 +594,7 @@ void tdx_get_ve_info(struct ve_info *ve)
 	 * Note, the TDX module treats virtual NMIs as inhibited if the #VE
 	 * valid flag is set. It means that NMI=>#VE will not result in a #DF.
 	 */
-	tdx_module_call(TDG_VP_VEINFO_GET, 0, 0, 0, 0, &out);
+	tdcall(TDG_VP_VEINFO_GET, 0, 0, 0, 0, &out);
 
 	/* Transfer the output parameters */
 	ve->exit_reason = out.rcx;
@@ -774,7 +774,7 @@ void __init tdx_early_init(void)
 	cc_set_mask(cc_mask);
 
 	/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
-	tdx_module_call(TDG_VM_WR, 0, TDCS_NOTIFY_ENABLES, 0, -1ULL, NULL);
+	tdcall(TDG_VM_WR, 0, TDCS_NOTIFY_ENABLES, 0, -1ULL, NULL);
 
 	/*
 	 * All bits above GPA width are reserved and kernel treats shared bit
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index 78f109446da6..9e3699b751ef 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -88,8 +88,8 @@ struct tdx_module_output {
 };
 
 /* Used to communicate with the TDX module */
-u64 __tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
-		      struct tdx_module_output *out);
+u64 __tdcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
+	     struct tdx_module_output *out);
 
 bool tdx_accept_memory(phys_addr_t start, phys_addr_t end);
 
-- 
2.41.0

[PATCH v2 05/11] x86/tdx: Pass TDCALL/SEAMCALL input/output registers via a structure

[Kai Huang]

Currently, the TDX_MODULE_CALL asm macro, which handles both TDCALL and
SEAMCALL, takes one parameter for each input register and an optional
'struct tdx_module_output' (a collection of output registers) as output.
This is different from the TDX_HYPERCALL macro which uses a single
'struct tdx_hypercall_args' to carry all input/output registers.

The newer TDX versions introduce more TDCALLs/SEAMCALLs which use more
input/output registers.  Also, the TDH.VP.ENTER (which isn't covered
by the current TDX_MODULE_CALL macro) basically can use all registers
that the TDX_HYPERCALL does.  The current TDX_MODULE_CALL macro isn't
extendible to cover those cases.

Similar to the TDX_HYPERCALL macro, simplify the TDX_MODULE_CALL macro
to use a single structure 'struct tdx_module_args' to carry all the
input/output registers.

Currently, the TDX_MODULE_CALL macro depends on the caller to pass a
non-NULL 'struct tdx_module_output' to get additional output registers.
Similar to the TDX_HYPERCALL macro, change the TDX_MODULE_CALL macro to
take a new 'ret' macro argument to indicate whether to save the output
registers to the 'struct tdx_module_args'.  Also introduce a new
__tdcall_ret() for that purpose, similar to the __tdx_hypercall_ret().

Note the tdcall(), which is a wrapper of __tdcall(), is called by three
callers: tdx_parse_tdinfo(), tdx_get_ve_info() and tdx_early_init().
The former two need the additional output but the last one doesn't.  For
simplicity, make tdcall() always call __tdcall_ret() to avoid another
"_ret()" wrapper.  The last caller tdx_early_init() isn't performance
critical anyway.

Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kai Huang <kai.huang@intel.com>
---

v1 -> v2:
 - Code change due to patch 02.
 - Minor improvement in comments and changelog.

---
 arch/x86/coco/tdx/tdcall.S        | 47 ++++++----------
 arch/x86/coco/tdx/tdx-shared.c    |  6 +-
 arch/x86/coco/tdx/tdx.c           | 44 ++++++++-------
 arch/x86/include/asm/shared/tdx.h | 10 ++--
 arch/x86/kernel/asm-offsets.c     | 12 ++--
 arch/x86/virt/vmx/tdx/tdxcall.S   | 93 ++++++++++++-------------------
 6 files changed, 95 insertions(+), 117 deletions(-)

diff --git a/arch/x86/coco/tdx/tdcall.S b/arch/x86/coco/tdx/tdcall.S
index 6aebac08f2bf..56b9cd32895e 100644
--- a/arch/x86/coco/tdx/tdcall.S
+++ b/arch/x86/coco/tdx/tdcall.S
@@ -43,37 +43,10 @@
  * __tdcall()  - Used by TDX guests to request services from the TDX
  * module (does not include VMM services) using TDCALL instruction.
  *
- * Transforms function call register arguments into the TDCALL register ABI.
- * After TDCALL operation, TDX module output is saved in @out (if it is
- * provided by the user).
- *
- *-------------------------------------------------------------------------
- * TDCALL ABI:
- *-------------------------------------------------------------------------
- * Input Registers:
- *
- * RAX                 - TDCALL Leaf number.
- * RCX,RDX,R8-R9       - TDCALL Leaf specific input registers.
- *
- * Output Registers:
- *
- * RAX                 - TDCALL instruction error code.
- * RCX,RDX,R8-R11      - TDCALL Leaf specific output registers.
- *
- *-------------------------------------------------------------------------
- *
  * __tdcall() function ABI:
  *
- * @fn  (RDI)          - TDCALL Leaf ID,    moved to RAX
- * @rcx (RSI)          - Input parameter 1, moved to RCX
- * @rdx (RDX)          - Input parameter 2, moved to RDX
- * @r8  (RCX)          - Input parameter 3, moved to R8
- * @r9  (R8)           - Input parameter 4, moved to R9
- *
- * @out (R9)           - struct tdx_module_output pointer
- *                       stored temporarily in R12 (not
- *                       shared with the TDX module). It
- *                       can be NULL.
+ * @fn   (RDI)	- TDCALL Leaf ID, moved to RAX
+ * @args (RSI)	- struct tdx_module_args for input
  *
  * Return status of TDCALL via RAX.
  */
@@ -81,6 +54,22 @@ SYM_FUNC_START(__tdcall)
 	TDX_MODULE_CALL host=0
 SYM_FUNC_END(__tdcall)
 
+/*
+ * __tdcall_ret() - Used by TDX guests to request services from the TDX
+ * module (does not include VMM services) using TDCALL instruction, with
+ * saving output registers to the 'struct tdx_module_args' used as input.
+ *
+ * __tdcall_ret() function ABI:
+ *
+ * @fn   (RDI)	- TDCALL Leaf ID, moved to RAX
+ * @args (RSI)	- struct tdx_module_args for input and output
+ *
+ * Return status of TDCALL via RAX.
+ */
+SYM_FUNC_START(__tdcall_ret)
+	TDX_MODULE_CALL host=0 ret=1
+SYM_FUNC_END(__tdcall_ret)
+
 /*
  * TDX_HYPERCALL - Make hypercalls to a TDX VMM using TDVMCALL leaf of TDCALL
  * instruction
diff --git a/arch/x86/coco/tdx/tdx-shared.c b/arch/x86/coco/tdx/tdx-shared.c
index 90631abdac34..a7396d0ddef9 100644
--- a/arch/x86/coco/tdx/tdx-shared.c
+++ b/arch/x86/coco/tdx/tdx-shared.c
@@ -5,7 +5,7 @@ static unsigned long try_accept_one(phys_addr_t start, unsigned long len,
 				    enum pg_level pg_level)
 {
 	unsigned long accept_size = page_level_size(pg_level);
-	u64 tdcall_rcx;
+	struct tdx_module_args args = {};
 	u8 page_size;
 
 	if (!IS_ALIGNED(start, accept_size))
@@ -34,8 +34,8 @@ static unsigned long try_accept_one(phys_addr_t start, unsigned long len,
 		return 0;
 	}
 
-	tdcall_rcx = start | page_size;
-	if (__tdcall(TDG_MEM_PAGE_ACCEPT, tdcall_rcx, 0, 0, 0, NULL))
+	args.rcx = start | page_size;
+	if (__tdcall(TDG_MEM_PAGE_ACCEPT, &args))
 		return 0;
 
 	return accept_size;
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 8c13944925e3..2e19cc62e59e 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -66,10 +66,9 @@ EXPORT_SYMBOL_GPL(tdx_kvm_hypercall);
  * should only be used for calls that have no legitimate reason to fail
  * or where the kernel can not survive the call failing.
  */
-static inline void tdcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
-			  struct tdx_module_output *out)
+static inline void tdcall(u64 fn, struct tdx_module_args *args)
 {
-	if (__tdcall(fn, rcx, rdx, r8, r9, out))
+	if (__tdcall_ret(fn, args))
 		panic("TDCALL %lld failed (Buggy TDX module!)\n", fn);
 }
 
@@ -89,11 +88,14 @@ static inline void tdcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
  */
 int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport)
 {
+	struct tdx_module_args args = {
+		.rcx = virt_to_phys(tdreport),
+		.rdx = virt_to_phys(reportdata),
+		.r8 = TDREPORT_SUBTYPE_0,
+	};
 	u64 ret;
 
-	ret = __tdcall(TDG_MR_REPORT, virt_to_phys(tdreport),
-			virt_to_phys(reportdata), TDREPORT_SUBTYPE_0,
-			0, NULL);
+	ret = __tdcall(TDG_MR_REPORT, &args);
 	if (ret) {
 		if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
 			return -EINVAL;
@@ -141,7 +143,7 @@ static void __noreturn tdx_panic(const char *msg)
 
 static void tdx_parse_tdinfo(u64 *cc_mask)
 {
-	struct tdx_module_output out;
+	struct tdx_module_args args = {};
 	unsigned int gpa_width;
 	u64 td_attr;
 
@@ -152,7 +154,7 @@ static void tdx_parse_tdinfo(u64 *cc_mask)
 	 * Guest-Host-Communication Interface (GHCI), section 2.4.2 TDCALL
 	 * [TDG.VP.INFO].
 	 */
-	tdcall(TDG_VP_INFO, 0, 0, 0, 0, &out);
+	tdcall(TDG_VP_INFO, &args);
 
 	/*
 	 * The highest bit of a guest physical address is the "sharing" bit.
@@ -161,7 +163,7 @@ static void tdx_parse_tdinfo(u64 *cc_mask)
 	 * The GPA width that comes out of this call is critical. TDX guests
 	 * can not meaningfully run without it.
 	 */
-	gpa_width = out.rcx & GENMASK(5, 0);
+	gpa_width = args.rcx & GENMASK(5, 0);
 	*cc_mask = BIT_ULL(gpa_width - 1);
 
 	/*
@@ -169,7 +171,7 @@ static void tdx_parse_tdinfo(u64 *cc_mask)
 	 * memory.  Ensure that no #VE will be delivered for accesses to
 	 * TD-private memory.  Only VMM-shared memory (MMIO) will #VE.
 	 */
-	td_attr = out.rdx;
+	td_attr = args.rdx;
 	if (!(td_attr & ATTR_SEPT_VE_DISABLE)) {
 		const char *msg = "TD misconfiguration: SEPT_VE_DISABLE attribute must be set.";
 
@@ -577,7 +579,7 @@ __init bool tdx_early_handle_ve(struct pt_regs *regs)
 
 void tdx_get_ve_info(struct ve_info *ve)
 {
-	struct tdx_module_output out;
+	struct tdx_module_args args = {};
 
 	/*
 	 * Called during #VE handling to retrieve the #VE info from the
@@ -594,15 +596,15 @@ void tdx_get_ve_info(struct ve_info *ve)
 	 * Note, the TDX module treats virtual NMIs as inhibited if the #VE
 	 * valid flag is set. It means that NMI=>#VE will not result in a #DF.
 	 */
-	tdcall(TDG_VP_VEINFO_GET, 0, 0, 0, 0, &out);
+	tdcall(TDG_VP_VEINFO_GET, &args);
 
 	/* Transfer the output parameters */
-	ve->exit_reason = out.rcx;
-	ve->exit_qual   = out.rdx;
-	ve->gla         = out.r8;
-	ve->gpa         = out.r9;
-	ve->instr_len   = lower_32_bits(out.r10);
-	ve->instr_info  = upper_32_bits(out.r10);
+	ve->exit_reason = args.rcx;
+	ve->exit_qual   = args.rdx;
+	ve->gla         = args.r8;
+	ve->gpa         = args.r9;
+	ve->instr_len   = lower_32_bits(args.r10);
+	ve->instr_info  = upper_32_bits(args.r10);
 }
 
 /*
@@ -759,6 +761,10 @@ static bool tdx_enc_status_change_finish(unsigned long vaddr, int numpages,
 
 void __init tdx_early_init(void)
 {
+	struct tdx_module_args args = {
+		.rdx = TDCS_NOTIFY_ENABLES,
+		.r9 = -1ULL,
+	};
 	u64 cc_mask;
 	u32 eax, sig[3];
 
@@ -774,7 +780,7 @@ void __init tdx_early_init(void)
 	cc_set_mask(cc_mask);
 
 	/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
-	tdcall(TDG_VM_WR, 0, TDCS_NOTIFY_ENABLES, 0, -1ULL, NULL);
+	tdcall(TDG_VM_WR, &args);
 
 	/*
 	 * All bits above GPA width are reserved and kernel treats shared bit
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index 9e3699b751ef..1d338a401b88 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -74,22 +74,24 @@ static inline u64 _tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14, u64 r15)
 void __tdx_hypercall_failed(void);
 
 /*
- * Used in __tdx_module_call() to gather the output registers' values of the
+ * Used in __tdcall*() to gather the input/output registers' values of the
  * TDCALL instruction when requesting services from the TDX module. This is a
  * software only structure and not part of the TDX module/VMM ABI
  */
-struct tdx_module_output {
+struct tdx_module_args {
+	/* input/output */
 	u64 rcx;
 	u64 rdx;
 	u64 r8;
 	u64 r9;
+	/* additional output */
 	u64 r10;
 	u64 r11;
 };
 
 /* Used to communicate with the TDX module */
-u64 __tdcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
-	     struct tdx_module_output *out);
+u64 __tdcall(u64 fn, struct tdx_module_args *args);
+u64 __tdcall_ret(u64 fn, struct tdx_module_args *args);
 
 bool tdx_accept_memory(phys_addr_t start, phys_addr_t end);
 
diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index dc3576303f1a..50383bc46dd7 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -68,12 +68,12 @@ static void __used common(void)
 #endif
 
 	BLANK();
-	OFFSET(TDX_MODULE_rcx, tdx_module_output, rcx);
-	OFFSET(TDX_MODULE_rdx, tdx_module_output, rdx);
-	OFFSET(TDX_MODULE_r8,  tdx_module_output, r8);
-	OFFSET(TDX_MODULE_r9,  tdx_module_output, r9);
-	OFFSET(TDX_MODULE_r10, tdx_module_output, r10);
-	OFFSET(TDX_MODULE_r11, tdx_module_output, r11);
+	OFFSET(TDX_MODULE_rcx, tdx_module_args, rcx);
+	OFFSET(TDX_MODULE_rdx, tdx_module_args, rdx);
+	OFFSET(TDX_MODULE_r8,  tdx_module_args, r8);
+	OFFSET(TDX_MODULE_r9,  tdx_module_args, r9);
+	OFFSET(TDX_MODULE_r10, tdx_module_args, r10);
+	OFFSET(TDX_MODULE_r11, tdx_module_args, r11);
 
 	BLANK();
 	OFFSET(TDX_HYPERCALL_r8,  tdx_hypercall_args, r8);
diff --git a/arch/x86/virt/vmx/tdx/tdxcall.S b/arch/x86/virt/vmx/tdx/tdxcall.S
index 6bdf6e137953..a0e7fe81bf63 100644
--- a/arch/x86/virt/vmx/tdx/tdxcall.S
+++ b/arch/x86/virt/vmx/tdx/tdxcall.S
@@ -17,34 +17,33 @@
  *            TDX module and hypercalls to the VMM.
  * SEAMCALL - used by TDX hosts to make requests to the
  *            TDX module.
+ *
+ *-------------------------------------------------------------------------
+ * TDCALL/SEAMCALL ABI:
+ *-------------------------------------------------------------------------
+ * Input Registers:
+ *
+ * RAX                 - TDCALL/SEAMCALL Leaf number.
+ * RCX,RDX,R8-R9       - TDCALL/SEAMCALL Leaf specific input registers.
+ *
+ * Output Registers:
+ *
+ * RAX                 - TDCALL/SEAMCALL instruction error code.
+ * RCX,RDX,R8-R11      - TDCALL/SEAMCALL Leaf specific output registers.
+ *
+ *-------------------------------------------------------------------------
  */
-.macro TDX_MODULE_CALL host:req
+.macro TDX_MODULE_CALL host:req ret=0
 	FRAME_BEGIN
-	/*
-	 * R12 will be used as temporary storage for struct tdx_module_output
-	 * pointer. Since R12-R15 registers are not used by TDCALL/SEAMCALL
-	 * services supported by this function, it can be reused.
-	 */
-
-	/* Callee saved, so preserve it */
-	push %r12
-
-	/*
-	 * Push output pointer to stack.
-	 * After the operation, it will be fetched into R12 register.
-	 */
-	push %r9
 
-	/* Mangle function call ABI into TDCALL/SEAMCALL ABI: */
 	/* Move Leaf ID to RAX */
 	mov %rdi, %rax
-	/* Move input 4 to R9 */
-	mov %r8,  %r9
-	/* Move input 3 to R8 */
-	mov %rcx, %r8
-	/* Move input 1 to RCX */
-	mov %rsi, %rcx
-	/* Leave input param 2 in RDX */
+
+	/* Move other input regs from 'struct tdx_module_args' */
+	movq	TDX_MODULE_rcx(%rsi), %rcx
+	movq	TDX_MODULE_rdx(%rsi), %rdx
+	movq	TDX_MODULE_r8(%rsi), %r8
+	movq	TDX_MODULE_r9(%rsi), %r9
 
 .if \host
 	seamcall
@@ -59,49 +58,31 @@
 	 * This value will never be used as actual SEAMCALL error code as
 	 * it is from the Reserved status code class.
 	 */
-	jc .Lseamcall_vmfailinvalid
+	jc .Lseamcall_vmfailinvalid\@
 .else
 	tdcall
 .endif
 
-	/*
-	 * Fetch output pointer from stack to R12 (It is used
-	 * as temporary storage)
-	 */
-	pop %r12
-
-	/*
-	 * Since this macro can be invoked with NULL as an output pointer,
-	 * check if caller provided an output struct before storing output
-	 * registers.
-	 *
-	 * Update output registers, even if the call failed (RAX != 0).
-	 * Other registers may contain details of the failure.
-	 */
-	test %r12, %r12
-	jz .Lout
-
-	/* Copy result registers to output struct: */
-	movq %rcx, TDX_MODULE_rcx(%r12)
-	movq %rdx, TDX_MODULE_rdx(%r12)
-	movq %r8,  TDX_MODULE_r8(%r12)
-	movq %r9,  TDX_MODULE_r9(%r12)
-	movq %r10, TDX_MODULE_r10(%r12)
-	movq %r11, TDX_MODULE_r11(%r12)
-
-.Lout:
-	/* Restore the state of R12 register */
-	pop %r12
+.if \ret
+	/* Copy output registers to the structure */
+	movq %rcx, TDX_MODULE_rcx(%rsi)
+	movq %rdx, TDX_MODULE_rdx(%rsi)
+	movq %r8,  TDX_MODULE_r8(%rsi)
+	movq %r9,  TDX_MODULE_r9(%rsi)
+	movq %r10, TDX_MODULE_r10(%rsi)
+	movq %r11, TDX_MODULE_r11(%rsi)
+.endif
 
+.if \host
+.Lout\@:
+.endif
 	FRAME_END
 	RET
 
 .if \host
-.Lseamcall_vmfailinvalid:
+.Lseamcall_vmfailinvalid\@:
 	mov $TDX_SEAMCALL_VMFAILINVALID, %rax
-	/* pop the unused output pointer back to %r9 */
-	pop %r9
-	jmp .Lout
+	jmp .Lout\@
 .endif	/* \host */
 
 .endm
-- 
2.41.0

[PATCH v2 06/11] x86/tdx: Extend TDX_MODULE_CALL to support more TDCALL/SEAMCALL leafs

[Kai Huang]

The TDX guest live migration support (TDX 1.5) adds new TDCALL/SEAMCALL
leaf functions.  Those new TDCALLs/SEAMCALLs take additional registers
for input (R10-R13) and output (R12-R13).  TDG.SERVTD.RD is an example.

Also, the current TDX_MODULE_CALL doesn't aim to handle TDH.VP.ENTER
SEAMCALL, which monitors the TDG.VP.VMCALL in input/output registers
when it returns in case of VMCALL from TDX guest.

With those new TDCALLs/SEAMCALLs and the TDH.VP.ENTER covered, the
TDX_MODULE_CALL macro basically needs to handle the same input/output
registers as the TDX_HYPERCALL does.  And as a result, they also share
similar logic in the assembly, thus should be unified to use one common
assembly.

Extend the TDX_MODULE_CALL asm to support the new TDCALLs/SEAMCALLs and
also the TDH.VP.ENTER SEAMCALL.  Eventually it will be unified with the
TDX_HYPERCALL.

The new input/output registers fit with the "callee-saved" registers in
the x86 calling convention.  Add a new "saved" parameter to support
those new TDCALLs/SEAMCALLs and TDH.VP.ENTER and keep the existing
TDCALLs/SEAMCALLs minimally impacted.

For TDH.VP.ENTER, after it returns the registers shared by the guest
contain guest's values.  Explicitly clear them to prevent speculative
use of guest's values.

Note most TDX live migration related SEAMCALLs may also clobber AVX*
state ("AVX, AVX2 and AVX512 state: may be reset to the architectural
INIT state" -- see TDH.EXPORT.MEM for example).  And TDH.VP.ENTER also
clobbers XMM0-XMM15 when the corresponding bit is set in RCX.  Don't
handle them in the TDX_MODULE_CALL macro but let the caller save and
restore when needed.

This is basically based on Peter's code.

Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kai Huang <kai.huang@intel.com>
---

v1 -> v2:
 - xorq %rcx, %rcx -> xorl %eax, %eax to save the REX prefix
 - Minor improvement in comments and changelog.

---
 arch/x86/coco/tdx/tdcall.S        |   4 +
 arch/x86/include/asm/shared/tdx.h |  12 ++-
 arch/x86/kernel/asm-offsets.c     |   7 ++
 arch/x86/virt/vmx/tdx/tdxcall.S   | 126 ++++++++++++++++++++++++++++--
 4 files changed, 141 insertions(+), 8 deletions(-)

diff --git a/arch/x86/coco/tdx/tdcall.S b/arch/x86/coco/tdx/tdcall.S
index 56b9cd32895e..faf731d2b66a 100644
--- a/arch/x86/coco/tdx/tdcall.S
+++ b/arch/x86/coco/tdx/tdcall.S
@@ -48,6 +48,8 @@
  * @fn   (RDI)	- TDCALL Leaf ID, moved to RAX
  * @args (RSI)	- struct tdx_module_args for input
  *
+ * Only RCX/RDX/R8-R11 are used as input registers.
+ *
  * Return status of TDCALL via RAX.
  */
 SYM_FUNC_START(__tdcall)
@@ -64,6 +66,8 @@ SYM_FUNC_END(__tdcall)
  * @fn   (RDI)	- TDCALL Leaf ID, moved to RAX
  * @args (RSI)	- struct tdx_module_args for input and output
  *
+ * Only RCX/RDX/R8-R11 are used as input/output registers.
+ *
  * Return status of TDCALL via RAX.
  */
 SYM_FUNC_START(__tdcall_ret)
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index 1d338a401b88..4468988adec5 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -79,14 +79,22 @@ void __tdx_hypercall_failed(void);
  * software only structure and not part of the TDX module/VMM ABI
  */
 struct tdx_module_args {
-	/* input/output */
+	/* callee-clobbered */
 	u64 rcx;
 	u64 rdx;
 	u64 r8;
 	u64 r9;
-	/* additional output */
+	/* extra callee-clobbered */
 	u64 r10;
 	u64 r11;
+	/* callee-saved + rdi/rsi */
+	u64 r12;
+	u64 r13;
+	u64 r14;
+	u64 r15;
+	u64 rbx;
+	u64 rdi;
+	u64 rsi;
 };
 
 /* Used to communicate with the TDX module */
diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index 50383bc46dd7..1581564a67b7 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -74,6 +74,13 @@ static void __used common(void)
 	OFFSET(TDX_MODULE_r9,  tdx_module_args, r9);
 	OFFSET(TDX_MODULE_r10, tdx_module_args, r10);
 	OFFSET(TDX_MODULE_r11, tdx_module_args, r11);
+	OFFSET(TDX_MODULE_r12, tdx_module_args, r12);
+	OFFSET(TDX_MODULE_r13, tdx_module_args, r13);
+	OFFSET(TDX_MODULE_r14, tdx_module_args, r14);
+	OFFSET(TDX_MODULE_r15, tdx_module_args, r15);
+	OFFSET(TDX_MODULE_rbx, tdx_module_args, rbx);
+	OFFSET(TDX_MODULE_rdi, tdx_module_args, rdi);
+	OFFSET(TDX_MODULE_rsi, tdx_module_args, rsi);
 
 	BLANK();
 	OFFSET(TDX_HYPERCALL_r8,  tdx_hypercall_args, r8);
diff --git a/arch/x86/virt/vmx/tdx/tdxcall.S b/arch/x86/virt/vmx/tdx/tdxcall.S
index a0e7fe81bf63..42f9225a530d 100644
--- a/arch/x86/virt/vmx/tdx/tdxcall.S
+++ b/arch/x86/virt/vmx/tdx/tdxcall.S
@@ -23,17 +23,25 @@
  *-------------------------------------------------------------------------
  * Input Registers:
  *
- * RAX                 - TDCALL/SEAMCALL Leaf number.
- * RCX,RDX,R8-R9       - TDCALL/SEAMCALL Leaf specific input registers.
+ * RAX                        - TDCALL/SEAMCALL Leaf number.
+ * RCX,RDX,RDI,RSI,RBX,R8-R15 - TDCALL/SEAMCALL Leaf specific input registers.
  *
  * Output Registers:
  *
- * RAX                 - TDCALL/SEAMCALL instruction error code.
- * RCX,RDX,R8-R11      - TDCALL/SEAMCALL Leaf specific output registers.
+ * RAX                        - TDCALL/SEAMCALL Leaf number.
+ * RCX,RDX,RDI,RSI,RBX,R8-R15 - TDCALL/SEAMCALL Leaf specific output registers.
  *
  *-------------------------------------------------------------------------
+ *
+ * So while the common core (RAX,RCX,RDX,R8-R11) fits nicely in the
+ * callee-clobbered registers and even leaves RDI,RSI free to act as a
+ * base pointer, some leafs (e.g., VP.ENTER) make a giant mess of things.
+ *
+ * For simplicity, assume that anything that needs the callee-saved regs
+ * also tramples on RDI,RSI.  This isn't strictly true, see for example
+ * TDH.EXPORT.MEM.
  */
-.macro TDX_MODULE_CALL host:req ret=0
+.macro TDX_MODULE_CALL host:req ret=0 saved=0
 	FRAME_BEGIN
 
 	/* Move Leaf ID to RAX */
@@ -44,6 +52,37 @@
 	movq	TDX_MODULE_rdx(%rsi), %rdx
 	movq	TDX_MODULE_r8(%rsi), %r8
 	movq	TDX_MODULE_r9(%rsi), %r9
+	movq	TDX_MODULE_r10(%rsi), %r10
+	movq	TDX_MODULE_r11(%rsi), %r11
+
+.if \saved
+	/*
+	 * Move additional input regs from the structure.  For simplicity
+	 * assume that anything needs the callee-saved regs also tramples
+	 * on %rdi/%rsi (see VP.ENTER).
+	 */
+	/* Save those callee-saved GPRs as mandated by the x86_64 ABI */
+	pushq	%rbx
+	pushq	%r12
+	pushq	%r13
+	pushq	%r14
+	pushq	%r15
+
+	movq	TDX_MODULE_r12(%rsi), %r12
+	movq	TDX_MODULE_r13(%rsi), %r13
+	movq	TDX_MODULE_r14(%rsi), %r14
+	movq	TDX_MODULE_r15(%rsi), %r15
+	movq	TDX_MODULE_rbx(%rsi), %rbx
+
+.if \ret
+	/* Save the structure pointer as %rsi is about to be clobbered */
+	pushq	%rsi
+.endif
+
+	movq	TDX_MODULE_rdi(%rsi), %rdi
+	/* %rsi needs to be done at last */
+	movq	TDX_MODULE_rsi(%rsi), %rsi
+.endif	/* \saved */
 
 .if \host
 	seamcall
@@ -64,6 +103,37 @@
 .endif
 
 .if \ret
+.if \saved
+	/*
+	 * Restore the structure from stack to save the output registers
+	 *
+	 * In case of VP.ENTER returns due to TDVMCALL, all registers are
+	 * valid thus no register can be used as spare to restore the
+	 * structure from the stack (see "TDH.VP.ENTER Output Operands
+	 * Definition on TDCALL(TDG.VP.VMCALL) Following a TD Entry").
+	 * For this case, need to make one register as spare by saving it
+	 * to the stack and then manually load the structure pointer to
+	 * the spare register.
+	 *
+	 * Note for other TDCALLs/SEAMCALLs there are spare registers
+	 * thus no need for such hack but just use this for all.
+	 */
+	pushq	%rax		/* save the TDCALL/SEAMCALL return code */
+	movq	8(%rsp), %rax	/* restore the structure pointer */
+	movq	%rsi, TDX_MODULE_rsi(%rax)	/* save %rsi */
+	movq	%rax, %rsi	/* use %rsi as structure pointer */
+	popq	%rax		/* restore the return code */
+	popq	%rsi		/* pop the structure pointer */
+
+	/* Copy additional output regs to the structure  */
+	movq %r12, TDX_MODULE_r12(%rsi)
+	movq %r13, TDX_MODULE_r13(%rsi)
+	movq %r14, TDX_MODULE_r14(%rsi)
+	movq %r15, TDX_MODULE_r15(%rsi)
+	movq %rbx, TDX_MODULE_rbx(%rsi)
+	movq %rdi, TDX_MODULE_rdi(%rsi)
+.endif	/* \saved */
+
 	/* Copy output registers to the structure */
 	movq %rcx, TDX_MODULE_rcx(%rsi)
 	movq %rdx, TDX_MODULE_rdx(%rsi)
@@ -71,17 +141,61 @@
 	movq %r9,  TDX_MODULE_r9(%rsi)
 	movq %r10, TDX_MODULE_r10(%rsi)
 	movq %r11, TDX_MODULE_r11(%rsi)
-.endif
+.endif	/* \ret */
+
+.if \host && \saved && \ret
+	/*
+	 * Clear registers shared by guest for VP.ENTER to prevent
+	 * speculative use of guest's values, including those are
+	 * restored from the stack.
+	 *
+	 * See arch/x86/kvm/vmx/vmenter.S:
+	 *
+	 * In theory, a L1 cache miss when restoring register from stack
+	 * could lead to speculative execution with guest's values.
+	 *
+	 * Note: RBP/RSP are not used as shared register.  RSI has been
+	 * restored already.
+	 *
+	 * XOR is cheap, thus unconditionally do for all leafs.
+	 */
+	xorl %ecx,  %ecx
+	xorl %edx,  %edx
+	xorl %r8d,  %r8d
+	xorl %r9d,  %r9d
+	xorl %r10d, %r10d
+	xorl %r11d, %r11d
+	xorl %r12d, %r12d
+	xorl %r13d, %r13d
+	xorl %r14d, %r14d
+	xorl %r15d, %r15d
+	xorl %ebx,  %ebx
+	xorl %edi,  %edi
+.endif	/* \host && \ret && \host */
 
 .if \host
 .Lout\@:
 .endif
+
+.if \saved
+	/* Restore callee-saved GPRs as mandated by the x86_64 ABI */
+	popq	%r15
+	popq	%r14
+	popq	%r13
+	popq	%r12
+	popq	%rbx
+.endif	/* \saved */
+
 	FRAME_END
 	RET
 
 .if \host
 .Lseamcall_vmfailinvalid\@:
 	mov $TDX_SEAMCALL_VMFAILINVALID, %rax
+.if \ret && \saved
+	/* pop the unused structure pointer back to %rsi */
+	popq %rsi
+.endif
 	jmp .Lout\@
 .endif	/* \host */
 
-- 
2.41.0

[PATCH v2 07/11] x86/tdx: Make TDX_HYPERCALL asm similar to TDX_MODULE_CALL

[Kai Huang]

Now the 'struct tdx_hypercall_args' and 'struct tdx_module_args' are
almost the same, and the TDX_HYPERCALL and TDX_MODULE_CALL asm macro
share similar code pattern too.  The __tdx_hypercall() and __tdcall()
should be unified to use the same assembly code.

As a preparation to unify them, simplify the TDX_HYPERCALL to make it
more like the TDX_MODULE_CALL.

The TDX_HYPERCALL takes the pointer of 'struct tdx_hypercall_args' as
function call argument, and does below extra things comparing to the
TDX_MODULE_CALL:

1) It sets RAX to 0 (TDG.VP.VMCALL leaf) internally;
2) It sets RCX to the (fixed) bitmap of shared registers internally;
3) It calls __tdx_hypercall_failed() internally (and panics) when the
   TDCALL instruction itself fails;
4) After TDCALL, it moves R10 to RAX to return the return code of the
   VMCALL leaf, regardless the '\ret' asm macro argument;

Firstly, change the TDX_HYPERCALL to take the same function call
arguments as the TDX_MODULE_CALL does: TDCALL leaf ID, and the pointer
to 'struct tdx_module_args'.  Then 1) and 2) can be moved to the
caller:

 - TDG.VP.VMCALL leaf ID can be passed via the function call argument;
 - 'struct tdx_module_args' is 'struct tdx_hypercall_args' + RCX, thus
   the bitmap of shared registers can be passed via RCX in the
   structure.

Secondly, to move 3) and 4) out of assembly, make the TDX_HYPERCALL
always save output registers to the structure.  The caller then can:

 - Call __tdx_hypercall_failed() when TDX_HYPERCALL returns error;
 - Return R10 in the structure as the return code of the VMCALL leaf;

With above changes, change the asm function from __tdx_hypercall() to
__tdcall_hypercall(), and reimplement __tdx_hypercall() as the C wrapper
of it.  This avoids having to add another wrapper of __tdx_hypercall()
(_tdx_hypercall() is already taken).

The __tdcall_hypercall() will be replaced with a __tdcall() variant in
a later commit as the final goal is to have one assembly to handle both
TDCALL and TDVMCALL.

Remove the __tdx_hypercall_ret() as __tdx_hypercall() already does so.

By changing __tdx_hypercall() to a C function, __tdx_hypercall_failed()
is no longer called from '.noinstr.text', thus remove the 'noinstr'
annotation and the 'instrumentation_begin()'.

Implement __tdx_hypercall() in tdx-shared.c so it can be shared with the
compressed code.

Opportunistically fix a checkpatch error complaining using space around
parenthesis '(' and ')' while moving the bitmap of shared registers to
<asm/shared/tdx.h>.

Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kai Huang <kai.huang@intel.com>
---

v1 -> v2:
 - The first patch (major) split from v1 "x86/tdx: Unify TDX_HYPERCALL
   and TDX_MODULE_CALL assembly"
 - Rebase to 6.5-rc2.
 - Removed 'noinstr' and 'instrumentation_begin()' in
   __tdx_hypercall_failed().
 - Minor improvement in comments and changelog.

---
 arch/x86/boot/compressed/tdx.c    |   2 +-
 arch/x86/coco/tdx/tdcall.S        | 148 ++++++++++--------------------
 arch/x86/coco/tdx/tdx-shared.c    |  43 +++++++++
 arch/x86/coco/tdx/tdx.c           |  13 ++-
 arch/x86/include/asm/shared/tdx.h |  86 +++++++++++------
 arch/x86/kernel/asm-offsets.c     |  14 ---
 6 files changed, 157 insertions(+), 149 deletions(-)

diff --git a/arch/x86/boot/compressed/tdx.c b/arch/x86/boot/compressed/tdx.c
index 8841b945a1e2..bc03eae2c560 100644
--- a/arch/x86/boot/compressed/tdx.c
+++ b/arch/x86/boot/compressed/tdx.c
@@ -26,7 +26,7 @@ static inline unsigned int tdx_io_in(int size, u16 port)
 		.r14 = port,
 	};
 
-	if (__tdx_hypercall_ret(&args))
+	if (__tdx_hypercall(&args))
 		return UINT_MAX;
 
 	return args.r11;
diff --git a/arch/x86/coco/tdx/tdcall.S b/arch/x86/coco/tdx/tdcall.S
index faf731d2b66a..086afe888e5e 100644
--- a/arch/x86/coco/tdx/tdcall.S
+++ b/arch/x86/coco/tdx/tdcall.S
@@ -10,33 +10,6 @@
 
 #include "../../virt/vmx/tdx/tdxcall.S"
 
-/*
- * Bitmasks of exposed registers (with VMM).
- */
-#define TDX_RDX		BIT(2)
-#define TDX_RBX		BIT(3)
-#define TDX_RSI		BIT(6)
-#define TDX_RDI		BIT(7)
-#define TDX_R8		BIT(8)
-#define TDX_R9		BIT(9)
-#define TDX_R10		BIT(10)
-#define TDX_R11		BIT(11)
-#define TDX_R12		BIT(12)
-#define TDX_R13		BIT(13)
-#define TDX_R14		BIT(14)
-#define TDX_R15		BIT(15)
-
-/*
- * These registers are clobbered to hold arguments for each
- * TDVMCALL. They are safe to expose to the VMM.
- * Each bit in this mask represents a register ID. Bit field
- * details can be found in TDX GHCI specification, section
- * titled "TDCALL [TDG.VP.VMCALL] leaf".
- */
-#define TDVMCALL_EXPOSE_REGS_MASK	\
-	( TDX_RDX | TDX_RBX | TDX_RSI | TDX_RDI | TDX_R8  | TDX_R9  | \
-	  TDX_R10 | TDX_R11 | TDX_R12 | TDX_R13 | TDX_R14 | TDX_R15 )
-
 .section .noinstr.text, "ax"
 
 /*
@@ -78,10 +51,13 @@ SYM_FUNC_END(__tdcall_ret)
  * TDX_HYPERCALL - Make hypercalls to a TDX VMM using TDVMCALL leaf of TDCALL
  * instruction
  *
- * Transforms values in  function call argument struct tdx_hypercall_args @args
+ * Transforms values in  function call argument struct tdx_module_args @args
  * into the TDCALL register ABI. After TDCALL operation, VMM output is saved
  * back in @args, if \ret is 1.
  *
+ * Depends on the caller to pass TDG.VP.VMCALL as the TDCALL leaf, and set
+ * @args::rcx to TDVMCALL_EXPOSE_REGS_MASK.
+ *
  *-------------------------------------------------------------------------
  * TD VMCALL ABI:
  *-------------------------------------------------------------------------
@@ -106,7 +82,7 @@ SYM_FUNC_END(__tdcall_ret)
  * R8-R15              - Same as above.
  *
  */
-.macro TDX_HYPERCALL ret:req
+.macro TDX_HYPERCALL
 	FRAME_BEGIN
 
 	/* Save callee-saved GPRs as mandated by the x86_64 ABI */
@@ -116,63 +92,52 @@ SYM_FUNC_END(__tdcall_ret)
 	push %r12
 	push %rbx
 
-	/* Free RDI to be used as TDVMCALL arguments */
+	/* Move Leaf ID to RAX */
 	movq %rdi, %rax
 
+	/* Move bitmap of shared registers to RCX */
+	movq TDX_MODULE_rcx(%rsi), %rcx
+
 	/* Copy hypercall registers from arg struct: */
-	movq TDX_HYPERCALL_r8(%rax),  %r8
-	movq TDX_HYPERCALL_r9(%rax),  %r9
-	movq TDX_HYPERCALL_r10(%rax), %r10
-	movq TDX_HYPERCALL_r11(%rax), %r11
-	movq TDX_HYPERCALL_r12(%rax), %r12
-	movq TDX_HYPERCALL_r13(%rax), %r13
-	movq TDX_HYPERCALL_r14(%rax), %r14
-	movq TDX_HYPERCALL_r15(%rax), %r15
-	movq TDX_HYPERCALL_rdi(%rax), %rdi
-	movq TDX_HYPERCALL_rsi(%rax), %rsi
-	movq TDX_HYPERCALL_rbx(%rax), %rbx
-	movq TDX_HYPERCALL_rdx(%rax), %rdx
-
-	push %rax
-
-	/* Mangle function call ABI into TDCALL ABI: */
-	/* Set TDCALL leaf ID (TDVMCALL (0)) in RAX */
-	xor %eax, %eax
-
-	movl $TDVMCALL_EXPOSE_REGS_MASK, %ecx
+	movq TDX_MODULE_r8(%rsi),  %r8
+	movq TDX_MODULE_r9(%rsi),  %r9
+	movq TDX_MODULE_r10(%rsi), %r10
+	movq TDX_MODULE_r11(%rsi), %r11
+	movq TDX_MODULE_r12(%rsi), %r12
+	movq TDX_MODULE_r13(%rsi), %r13
+	movq TDX_MODULE_r14(%rsi), %r14
+	movq TDX_MODULE_r15(%rsi), %r15
+	movq TDX_MODULE_rdi(%rsi), %rdi
+	movq TDX_MODULE_rbx(%rsi), %rbx
+	movq TDX_MODULE_rdx(%rsi), %rdx
+
+	pushq %rsi
+	movq TDX_MODULE_rsi(%rsi), %rsi
 
 	tdcall
 
 	/*
-	 * RAX!=0 indicates a failure of the TDVMCALL mechanism itself and that
-	 * something has gone horribly wrong with the TDX module.
+	 * Restore the pointer of the structure to save output registers.
 	 *
-	 * The return status of the hypercall operation is in a separate
-	 * register (in R10). Hypercall errors are a part of normal operation
-	 * and are handled by callers.
+	 * RCX is used as bitmap of shared registers and doesn't hold any
+	 * value provided by the VMM, thus it can be used as spare to
+	 * restore the structure pointer.
 	 */
-	testq %rax, %rax
-	jne .Lpanic\@
-
-	pop %rax
-
-	.if \ret
-	movq %r8,  TDX_HYPERCALL_r8(%rax)
-	movq %r9,  TDX_HYPERCALL_r9(%rax)
-	movq %r10, TDX_HYPERCALL_r10(%rax)
-	movq %r11, TDX_HYPERCALL_r11(%rax)
-	movq %r12, TDX_HYPERCALL_r12(%rax)
-	movq %r13, TDX_HYPERCALL_r13(%rax)
-	movq %r14, TDX_HYPERCALL_r14(%rax)
-	movq %r15, TDX_HYPERCALL_r15(%rax)
-	movq %rdi, TDX_HYPERCALL_rdi(%rax)
-	movq %rsi, TDX_HYPERCALL_rsi(%rax)
-	movq %rbx, TDX_HYPERCALL_rbx(%rax)
-	movq %rdx, TDX_HYPERCALL_rdx(%rax)
-	.endif
-
-	/* TDVMCALL leaf return code is in R10 */
-	movq %r10, %rax
+	popq %rcx
+	movq %rsi, TDX_MODULE_rsi(%rcx)
+	movq %rcx, %rsi
+
+	movq %r8,  TDX_MODULE_r8(%rsi)
+	movq %r9,  TDX_MODULE_r9(%rsi)
+	movq %r10, TDX_MODULE_r10(%rsi)
+	movq %r11, TDX_MODULE_r11(%rsi)
+	movq %r12, TDX_MODULE_r12(%rsi)
+	movq %r13, TDX_MODULE_r13(%rsi)
+	movq %r14, TDX_MODULE_r14(%rsi)
+	movq %r15, TDX_MODULE_r15(%rsi)
+	movq %rdi, TDX_MODULE_rdi(%rsi)
+	movq %rbx, TDX_MODULE_rbx(%rsi)
+	movq %rdx, TDX_MODULE_rdx(%rsi)
 
 	/*
 	 * Zero out registers exposed to the VMM to avoid speculative execution
@@ -198,33 +163,20 @@ SYM_FUNC_END(__tdcall_ret)
 	FRAME_END
 
 	RET
-.Lpanic\@:
-	call __tdx_hypercall_failed
-	/* __tdx_hypercall_failed never returns */
-	REACHABLE
-	jmp .Lpanic\@
 .endm
 
 /*
  *
- * __tdx_hypercall() function ABI:
- *
- * @args  (RDI)        - struct tdx_hypercall_args for input
- *
- * On successful completion, return the hypercall error code.
- */
-SYM_FUNC_START(__tdx_hypercall)
-	TDX_HYPERCALL ret=0
-SYM_FUNC_END(__tdx_hypercall)
-
-/*
+ * __tdcall_hypercall() function ABI:
  *
- * __tdx_hypercall_ret() function ABI:
+ * @fn   (RDI)	- TDCALL leaf ID, moved to RAX
+ * @args (RSI)	- struct tdx_module_args for input/output
  *
- * @args  (RDI)        - struct tdx_hypercall_args for input and output
+ * @fn and @args::rcx from the caller must be TDG_VP_VMCALL and
+ * TDVMCALL_EXPOSE_REGS_MASK respectively.
  *
  * On successful completion, return the hypercall error code.
  */
-SYM_FUNC_START(__tdx_hypercall_ret)
-	TDX_HYPERCALL ret=1
-SYM_FUNC_END(__tdx_hypercall_ret)
+SYM_FUNC_START(__tdcall_hypercall)
+	TDX_HYPERCALL
+SYM_FUNC_END(__tdcall_hypercall)
diff --git a/arch/x86/coco/tdx/tdx-shared.c b/arch/x86/coco/tdx/tdx-shared.c
index a7396d0ddef9..13139ee171c8 100644
--- a/arch/x86/coco/tdx/tdx-shared.c
+++ b/arch/x86/coco/tdx/tdx-shared.c
@@ -69,3 +69,46 @@ bool tdx_accept_memory(phys_addr_t start, phys_addr_t end)
 
 	return true;
 }
+
+u64 __tdx_hypercall(struct tdx_hypercall_args *args)
+{
+	struct tdx_module_args margs = {
+		.rcx = TDVMCALL_EXPOSE_REGS_MASK,
+		.rdx = args->rdx,
+		.r8  = args->r8,
+		.r9  = args->r9,
+		.r10 = args->r10,
+		.r11 = args->r11,
+		.r12 = args->r12,
+		.r13 = args->r13,
+		.r14 = args->r14,
+		.r15 = args->r15,
+		.rbx = args->rbx,
+		.rdi = args->rdi,
+		.rsi = args->rsi,
+	};
+
+	/*
+	 * Failure of __tdcall_hypercall() indicates a failure of the TDVMCALL
+	 * mechanism itself and that something has gone horribly wrong with
+	 * the TDX module.  __tdx_hypercall_failed() never returns.
+	 */
+	if (__tdcall_hypercall(TDG_VP_VMCALL, &margs))
+		__tdx_hypercall_failed();
+
+	args->r8  = margs.r8;
+	args->r9  = margs.r9;
+	args->r10 = margs.r10;
+	args->r11 = margs.r11;
+	args->r12 = margs.r12;
+	args->r13 = margs.r13;
+	args->r14 = margs.r14;
+	args->r15 = margs.r15;
+	args->rdi = margs.rdi;
+	args->rsi = margs.rsi;
+	args->rbx = margs.rbx;
+	args->rdx = margs.rdx;
+
+	/* TDVMCALL leaf return code is in R10 */
+	return args->r10;
+}
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 2e19cc62e59e..aba58484ba10 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -37,10 +37,8 @@
 
 #define TDREPORT_SUBTYPE_0	0
 
-/* Called from __tdx_hypercall() for unrecoverable failure */
-noinstr void __tdx_hypercall_failed(void)
+void __tdx_hypercall_failed(void)
 {
-	instrumentation_begin();
 	panic("TDVMCALL failed. TDX module bug?");
 }
 
@@ -285,7 +283,7 @@ static int read_msr(struct pt_regs *regs, struct ve_info *ve)
 	 * can be found in TDX Guest-Host-Communication Interface
 	 * (GHCI), section titled "TDG.VP.VMCALL<Instruction.RDMSR>".
 	 */
-	if (__tdx_hypercall_ret(&args))
+	if (__tdx_hypercall(&args))
 		return -EIO;
 
 	regs->ax = lower_32_bits(args.r11);
@@ -339,7 +337,7 @@ static int handle_cpuid(struct pt_regs *regs, struct ve_info *ve)
 	 * ABI can be found in TDX Guest-Host-Communication Interface
 	 * (GHCI), section titled "VP.VMCALL<Instruction.CPUID>".
 	 */
-	if (__tdx_hypercall_ret(&args))
+	if (__tdx_hypercall(&args))
 		return -EIO;
 
 	/*
@@ -366,8 +364,9 @@ static bool mmio_read(int size, unsigned long addr, unsigned long *val)
 		.r15 = *val,
 	};
 
-	if (__tdx_hypercall_ret(&args))
+	if (__tdx_hypercall(&args))
 		return false;
+
 	*val = args.r11;
 	return true;
 }
@@ -500,7 +499,7 @@ static bool handle_in(struct pt_regs *regs, int size, int port)
 	 * in TDX Guest-Host-Communication Interface (GHCI) section titled
 	 * "TDG.VP.VMCALL<Instruction.IO>".
 	 */
-	success = !__tdx_hypercall_ret(&args);
+	success = !__tdx_hypercall(&args);
 
 	/* Update part of the register affected by the emulated instruction */
 	regs->ax &= ~mask;
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index 4468988adec5..da5205daa53d 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -11,6 +11,7 @@
 #define TDX_IDENT		"IntelTDX    "
 
 /* TDX module Call Leaf IDs */
+#define TDG_VP_VMCALL			0
 #define TDG_VP_INFO			1
 #define TDG_VP_VEINFO_GET		3
 #define TDG_MR_REPORT			4
@@ -24,8 +25,63 @@
 #define TDVMCALL_MAP_GPA		0x10001
 #define TDVMCALL_REPORT_FATAL_ERROR	0x10003
 
+/*
+ * Bitmasks of exposed registers (with VMM).
+ */
+#define TDX_RDX		BIT(2)
+#define TDX_RBX		BIT(3)
+#define TDX_RSI		BIT(6)
+#define TDX_RDI		BIT(7)
+#define TDX_R8		BIT(8)
+#define TDX_R9		BIT(9)
+#define TDX_R10		BIT(10)
+#define TDX_R11		BIT(11)
+#define TDX_R12		BIT(12)
+#define TDX_R13		BIT(13)
+#define TDX_R14		BIT(14)
+#define TDX_R15		BIT(15)
+
+/*
+ * These registers are clobbered to hold arguments for each
+ * TDVMCALL. They are safe to expose to the VMM.
+ * Each bit in this mask represents a register ID. Bit field
+ * details can be found in TDX GHCI specification, section
+ * titled "TDCALL [TDG.VP.VMCALL] leaf".
+ */
+#define TDVMCALL_EXPOSE_REGS_MASK	\
+	(TDX_RDX | TDX_RBX | TDX_RSI | TDX_RDI | TDX_R8  | TDX_R9  | \
+	 TDX_R10 | TDX_R11 | TDX_R12 | TDX_R13 | TDX_R14 | TDX_R15)
+
 #ifndef __ASSEMBLY__
 
+/*
+ * Used in __tdcall*() to gather the input/output registers' values of the
+ * TDCALL instruction when requesting services from the TDX module. This is a
+ * software only structure and not part of the TDX module/VMM ABI
+ */
+struct tdx_module_args {
+	/* callee-clobbered */
+	u64 rcx;
+	u64 rdx;
+	u64 r8;
+	u64 r9;
+	/* extra callee-clobbered */
+	u64 r10;
+	u64 r11;
+	/* callee-saved + rdi/rsi */
+	u64 r12;
+	u64 r13;
+	u64 r14;
+	u64 r15;
+	u64 rbx;
+	u64 rdi;
+	u64 rsi;
+};
+
+/* Used to communicate with the TDX module */
+u64 __tdcall(u64 fn, struct tdx_module_args *args);
+u64 __tdcall_ret(u64 fn, struct tdx_module_args *args);
+
 /*
  * Used in __tdx_hypercall() to pass down and get back registers' values of
  * the TDCALL instruction when requesting services from the VMM.
@@ -48,8 +104,8 @@ struct tdx_hypercall_args {
 };
 
 /* Used to request services from the VMM */
+u64 __tdcall_hypercall(u64 fn, struct tdx_module_args *args);
 u64 __tdx_hypercall(struct tdx_hypercall_args *args);
-u64 __tdx_hypercall_ret(struct tdx_hypercall_args *args);
 
 /*
  * Wrapper for standard use of __tdx_hypercall with no output aside from
@@ -73,34 +129,6 @@ static inline u64 _tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14, u64 r15)
 /* Called from __tdx_hypercall() for unrecoverable failure */
 void __tdx_hypercall_failed(void);
 
-/*
- * Used in __tdcall*() to gather the input/output registers' values of the
- * TDCALL instruction when requesting services from the TDX module. This is a
- * software only structure and not part of the TDX module/VMM ABI
- */
-struct tdx_module_args {
-	/* callee-clobbered */
-	u64 rcx;
-	u64 rdx;
-	u64 r8;
-	u64 r9;
-	/* extra callee-clobbered */
-	u64 r10;
-	u64 r11;
-	/* callee-saved + rdi/rsi */
-	u64 r12;
-	u64 r13;
-	u64 r14;
-	u64 r15;
-	u64 rbx;
-	u64 rdi;
-	u64 rsi;
-};
-
-/* Used to communicate with the TDX module */
-u64 __tdcall(u64 fn, struct tdx_module_args *args);
-u64 __tdcall_ret(u64 fn, struct tdx_module_args *args);
-
 bool tdx_accept_memory(phys_addr_t start, phys_addr_t end);
 
 /*
diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index 1581564a67b7..6913b372ccf7 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -82,20 +82,6 @@ static void __used common(void)
 	OFFSET(TDX_MODULE_rdi, tdx_module_args, rdi);
 	OFFSET(TDX_MODULE_rsi, tdx_module_args, rsi);
 
-	BLANK();
-	OFFSET(TDX_HYPERCALL_r8,  tdx_hypercall_args, r8);
-	OFFSET(TDX_HYPERCALL_r9,  tdx_hypercall_args, r9);
-	OFFSET(TDX_HYPERCALL_r10, tdx_hypercall_args, r10);
-	OFFSET(TDX_HYPERCALL_r11, tdx_hypercall_args, r11);
-	OFFSET(TDX_HYPERCALL_r12, tdx_hypercall_args, r12);
-	OFFSET(TDX_HYPERCALL_r13, tdx_hypercall_args, r13);
-	OFFSET(TDX_HYPERCALL_r14, tdx_hypercall_args, r14);
-	OFFSET(TDX_HYPERCALL_r15, tdx_hypercall_args, r15);
-	OFFSET(TDX_HYPERCALL_rdi, tdx_hypercall_args, rdi);
-	OFFSET(TDX_HYPERCALL_rsi, tdx_hypercall_args, rsi);
-	OFFSET(TDX_HYPERCALL_rbx, tdx_hypercall_args, rbx);
-	OFFSET(TDX_HYPERCALL_rdx, tdx_hypercall_args, rdx);
-
 	BLANK();
 	OFFSET(BP_scratch, boot_params, scratch);
 	OFFSET(BP_secure_boot, boot_params, secure_boot);
-- 
2.41.0

[PATCH v2 08/11] x86/tdx: Reimplement __tdx_hypercall() using TDX_MODULE_CALL asm

[Kai Huang]

Now the TDX_HYPERCALL asm is basically identical to the TDX_MODULE_CALL
with both '\saved' and '\ret' enabled, with two minor things though:

1) The way to restore the structure pointer is different

The TDX_HYPERCALL uses RCX as spare to restore the structure pointer,
but the TDX_MODULE_CALL assumes no spare register can be used.  In other
words, TDX_MODULE_CALL already covers what TDX_HYPERCALL does.

2) TDX_MODULE_CALL only clears shared registers for TDH.VP.ENTER

For this just need to make that code available for the non-host case.

Thus, remove the TDX_HYPERCALL and reimplement the __tdx_hypercall()
using the TDX_MODULE_CALL.

Extend the TDX_MODULE_CALL to cover "clear shared registers" for
TDG.VP.VMCALL.  Introduce a new __tdcall_saved_ret() to replace the
temporary __tdcall_hypercall().

The __tdcall_saved_ret() can also be used for those new TDCALLs which
require more input/output registers than the basic TDCALLs do.

Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kai Huang <kai.huang@intel.com>
---

v1 -> v2:
 - The second patch (new) split from v1 "x86/tdx: Unify TDX_HYPERCALL
   and TDX_MODULE_CALL assembly"
 - Rebase to 6.5-rc2.

---
 arch/x86/coco/tdx/tdcall.S        | 132 ++----------------------------
 arch/x86/coco/tdx/tdx-shared.c    |   4 +-
 arch/x86/include/asm/shared/tdx.h |   2 +-
 arch/x86/virt/vmx/tdx/tdxcall.S   |   8 +-
 4 files changed, 15 insertions(+), 131 deletions(-)

diff --git a/arch/x86/coco/tdx/tdcall.S b/arch/x86/coco/tdx/tdcall.S
index 086afe888e5e..21242c28b54b 100644
--- a/arch/x86/coco/tdx/tdcall.S
+++ b/arch/x86/coco/tdx/tdcall.S
@@ -48,135 +48,19 @@ SYM_FUNC_START(__tdcall_ret)
 SYM_FUNC_END(__tdcall_ret)
 
 /*
- * TDX_HYPERCALL - Make hypercalls to a TDX VMM using TDVMCALL leaf of TDCALL
- * instruction
- *
- * Transforms values in  function call argument struct tdx_module_args @args
- * into the TDCALL register ABI. After TDCALL operation, VMM output is saved
- * back in @args, if \ret is 1.
- *
- * Depends on the caller to pass TDG.VP.VMCALL as the TDCALL leaf, and set
- * @args::rcx to TDVMCALL_EXPOSE_REGS_MASK.
- *
- *-------------------------------------------------------------------------
- * TD VMCALL ABI:
- *-------------------------------------------------------------------------
- *
- * Input Registers:
- *
- * RAX                 - TDCALL instruction leaf number (0 - TDG.VP.VMCALL)
- * RCX                 - BITMAP which controls which part of TD Guest GPR
- *                       is passed as-is to the VMM and back.
- * R10                 - Set 0 to indicate TDCALL follows standard TDX ABI
- *                       specification. Non zero value indicates vendor
- *                       specific ABI.
- * R11                 - VMCALL sub function number
- * RBX, RDX, RDI, RSI  - Used to pass VMCALL sub function specific arguments.
- * R8-R9, R12-R15      - Same as above.
- *
- * Output Registers:
- *
- * RAX                 - TDCALL instruction status (Not related to hypercall
- *                        output).
- * RBX, RDX, RDI, RSI  - Hypercall sub function specific output values.
- * R8-R15              - Same as above.
- *
- */
-.macro TDX_HYPERCALL
-	FRAME_BEGIN
-
-	/* Save callee-saved GPRs as mandated by the x86_64 ABI */
-	push %r15
-	push %r14
-	push %r13
-	push %r12
-	push %rbx
-
-	/* Move Leaf ID to RAX */
-	movq %rdi, %rax
-
-	/* Move bitmap of shared registers to RCX */
-	movq TDX_MODULE_rcx(%rsi), %rcx
-
-	/* Copy hypercall registers from arg struct: */
-	movq TDX_MODULE_r8(%rsi),  %r8
-	movq TDX_MODULE_r9(%rsi),  %r9
-	movq TDX_MODULE_r10(%rsi), %r10
-	movq TDX_MODULE_r11(%rsi), %r11
-	movq TDX_MODULE_r12(%rsi), %r12
-	movq TDX_MODULE_r13(%rsi), %r13
-	movq TDX_MODULE_r14(%rsi), %r14
-	movq TDX_MODULE_r15(%rsi), %r15
-	movq TDX_MODULE_rdi(%rsi), %rdi
-	movq TDX_MODULE_rbx(%rsi), %rbx
-	movq TDX_MODULE_rdx(%rsi), %rdx
-
-	pushq %rsi
-	movq TDX_MODULE_rsi(%rsi), %rsi
-
-	tdcall
-
-	/*
-	 * Restore the pointer of the structure to save output registers.
-	 *
-	 * RCX is used as bitmap of shared registers and doesn't hold any
-	 * value provided by the VMM, thus it can be used as spare to
-	 * restore the structure pointer.
-	 */
-	popq %rcx
-	movq %rsi, TDX_MODULE_rsi(%rcx)
-	movq %rcx, %rsi
-
-	movq %r8,  TDX_MODULE_r8(%rsi)
-	movq %r9,  TDX_MODULE_r9(%rsi)
-	movq %r10, TDX_MODULE_r10(%rsi)
-	movq %r11, TDX_MODULE_r11(%rsi)
-	movq %r12, TDX_MODULE_r12(%rsi)
-	movq %r13, TDX_MODULE_r13(%rsi)
-	movq %r14, TDX_MODULE_r14(%rsi)
-	movq %r15, TDX_MODULE_r15(%rsi)
-	movq %rdi, TDX_MODULE_rdi(%rsi)
-	movq %rbx, TDX_MODULE_rbx(%rsi)
-	movq %rdx, TDX_MODULE_rdx(%rsi)
-
-	/*
-	 * Zero out registers exposed to the VMM to avoid speculative execution
-	 * with VMM-controlled values. This needs to include all registers
-	 * present in TDVMCALL_EXPOSE_REGS_MASK, except RBX, and R12-R15 which
-	 * will be restored.
-	 */
-	xor %r8d,  %r8d
-	xor %r9d,  %r9d
-	xor %r10d, %r10d
-	xor %r11d, %r11d
-	xor %rdi,  %rdi
-	xor %rsi,  %rsi
-	xor %rdx,  %rdx
-
-	/* Restore callee-saved GPRs as mandated by the x86_64 ABI */
-	pop %rbx
-	pop %r12
-	pop %r13
-	pop %r14
-	pop %r15
-
-	FRAME_END
-
-	RET
-.endm
-
-/*
+ * __tdcall_saved_ret() - Used by TDX guests to request services from the
+ * TDX module (including VMM services) using TDCALL instruction, with
+ * saving output registers to the 'struct tdx_module_args' used as input.
  *
- * __tdcall_hypercall() function ABI:
+ * __tdcall_saved_ret() function ABI:
  *
  * @fn   (RDI)	- TDCALL leaf ID, moved to RAX
  * @args (RSI)	- struct tdx_module_args for input/output
  *
- * @fn and @args::rcx from the caller must be TDG_VP_VMCALL and
- * TDVMCALL_EXPOSE_REGS_MASK respectively.
+ * All registers in @args are used as input/output registers.
  *
  * On successful completion, return the hypercall error code.
  */
-SYM_FUNC_START(__tdcall_hypercall)
-	TDX_HYPERCALL
-SYM_FUNC_END(__tdcall_hypercall)
+SYM_FUNC_START(__tdcall_saved_ret)
+	TDX_MODULE_CALL host=0 ret=1 saved=1
+SYM_FUNC_END(__tdcall_saved_ret)
diff --git a/arch/x86/coco/tdx/tdx-shared.c b/arch/x86/coco/tdx/tdx-shared.c
index 13139ee171c8..20e8794762e1 100644
--- a/arch/x86/coco/tdx/tdx-shared.c
+++ b/arch/x86/coco/tdx/tdx-shared.c
@@ -89,11 +89,11 @@ u64 __tdx_hypercall(struct tdx_hypercall_args *args)
 	};
 
 	/*
-	 * Failure of __tdcall_hypercall() indicates a failure of the TDVMCALL
+	 * Failure of __tdcall_saved_ret() indicates a failure of the TDVMCALL
 	 * mechanism itself and that something has gone horribly wrong with
 	 * the TDX module.  __tdx_hypercall_failed() never returns.
 	 */
-	if (__tdcall_hypercall(TDG_VP_VMCALL, &margs))
+	if (__tdcall_saved_ret(TDG_VP_VMCALL, &margs))
 		__tdx_hypercall_failed();
 
 	args->r8  = margs.r8;
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index da5205daa53d..188e8bf3332c 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -81,6 +81,7 @@ struct tdx_module_args {
 /* Used to communicate with the TDX module */
 u64 __tdcall(u64 fn, struct tdx_module_args *args);
 u64 __tdcall_ret(u64 fn, struct tdx_module_args *args);
+u64 __tdcall_saved_ret(u64 fn, struct tdx_module_args *args);
 
 /*
  * Used in __tdx_hypercall() to pass down and get back registers' values of
@@ -104,7 +105,6 @@ struct tdx_hypercall_args {
 };
 
 /* Used to request services from the VMM */
-u64 __tdcall_hypercall(u64 fn, struct tdx_module_args *args);
 u64 __tdx_hypercall(struct tdx_hypercall_args *args);
 
 /*
diff --git a/arch/x86/virt/vmx/tdx/tdxcall.S b/arch/x86/virt/vmx/tdx/tdxcall.S
index 42f9225a530d..3ed6d8b8d2a9 100644
--- a/arch/x86/virt/vmx/tdx/tdxcall.S
+++ b/arch/x86/virt/vmx/tdx/tdxcall.S
@@ -143,10 +143,10 @@
 	movq %r11, TDX_MODULE_r11(%rsi)
 .endif	/* \ret */
 
-.if \host && \saved && \ret
+.if \saved && \ret
 	/*
-	 * Clear registers shared by guest for VP.ENTER to prevent
-	 * speculative use of guest's values, including those are
+	 * Clear registers shared by guest for VP.VMCALL/VP.ENTER to prevent
+	 * speculative use of guest's/VMM's values, including those are
 	 * restored from the stack.
 	 *
 	 * See arch/x86/kvm/vmx/vmenter.S:
@@ -171,7 +171,7 @@
 	xorl %r15d, %r15d
 	xorl %ebx,  %ebx
 	xorl %edi,  %edi
-.endif	/* \host && \ret && \host */
+.endif	/* \ret && \host */
 
 .if \host
 .Lout\@:
-- 
2.41.0

[PATCH v2 09/11] x86/tdx: Remove 'struct tdx_hypercall_args'

[Kai Huang]

Now 'struct tdx_hypercall_args' is basically 'struct tdx_module_args'
minus RCX.  Although from __tdx_hypercall()'s perspective RCX isn't
used as shared register thus not part of input/output registers, it's
not worth to have a separate structure just due to one register.

Remove the 'struct tdx_hypercall_args' and use 'struct tdx_module_args'
instead in __tdx_hypercall() related code.  This also saves the memory
copy between the two structures within __tdx_hypercall().

Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kai Huang <kai.huang@intel.com>
---

v1 -> v2:
 - The third patch (new) split from v1 "x86/tdx: Unify TDX_HYPERCALL
   and TDX_MODULE_CALL assembly"
 - Rebase to 6.5-rc2.

---
 arch/x86/boot/compressed/tdx.c    |  4 ++--
 arch/x86/coco/tdx/tdx-shared.c    | 37 ++++++-------------------------
 arch/x86/coco/tdx/tdx.c           | 16 ++++++-------
 arch/x86/include/asm/shared/tdx.h | 25 ++-------------------
 4 files changed, 19 insertions(+), 63 deletions(-)

diff --git a/arch/x86/boot/compressed/tdx.c b/arch/x86/boot/compressed/tdx.c
index bc03eae2c560..8451d6a1030c 100644
--- a/arch/x86/boot/compressed/tdx.c
+++ b/arch/x86/boot/compressed/tdx.c
@@ -18,7 +18,7 @@ void __tdx_hypercall_failed(void)
 
 static inline unsigned int tdx_io_in(int size, u16 port)
 {
-	struct tdx_hypercall_args args = {
+	struct tdx_module_args args = {
 		.r10 = TDX_HYPERCALL_STANDARD,
 		.r11 = hcall_func(EXIT_REASON_IO_INSTRUCTION),
 		.r12 = size,
@@ -34,7 +34,7 @@ static inline unsigned int tdx_io_in(int size, u16 port)
 
 static inline void tdx_io_out(int size, u16 port, u32 value)
 {
-	struct tdx_hypercall_args args = {
+	struct tdx_module_args args = {
 		.r10 = TDX_HYPERCALL_STANDARD,
 		.r11 = hcall_func(EXIT_REASON_IO_INSTRUCTION),
 		.r12 = size,
diff --git a/arch/x86/coco/tdx/tdx-shared.c b/arch/x86/coco/tdx/tdx-shared.c
index 20e8794762e1..9b04959e6c5e 100644
--- a/arch/x86/coco/tdx/tdx-shared.c
+++ b/arch/x86/coco/tdx/tdx-shared.c
@@ -70,45 +70,22 @@ bool tdx_accept_memory(phys_addr_t start, phys_addr_t end)
 	return true;
 }
 
-u64 __tdx_hypercall(struct tdx_hypercall_args *args)
+u64 __tdx_hypercall(struct tdx_module_args *args)
 {
-	struct tdx_module_args margs = {
-		.rcx = TDVMCALL_EXPOSE_REGS_MASK,
-		.rdx = args->rdx,
-		.r8  = args->r8,
-		.r9  = args->r9,
-		.r10 = args->r10,
-		.r11 = args->r11,
-		.r12 = args->r12,
-		.r13 = args->r13,
-		.r14 = args->r14,
-		.r15 = args->r15,
-		.rbx = args->rbx,
-		.rdi = args->rdi,
-		.rsi = args->rsi,
-	};
+	/*
+	 * For TDVMCALL explicitly set RCX to the bitmap of shared registers.
+	 * The caller isn't expected to set @args->rcx anyway.
+	 */
+	args->rcx = TDVMCALL_EXPOSE_REGS_MASK;
 
 	/*
 	 * Failure of __tdcall_saved_ret() indicates a failure of the TDVMCALL
 	 * mechanism itself and that something has gone horribly wrong with
 	 * the TDX module.  __tdx_hypercall_failed() never returns.
 	 */
-	if (__tdcall_saved_ret(TDG_VP_VMCALL, &margs))
+	if (__tdcall_saved_ret(TDG_VP_VMCALL, args))
 		__tdx_hypercall_failed();
 
-	args->r8  = margs.r8;
-	args->r9  = margs.r9;
-	args->r10 = margs.r10;
-	args->r11 = margs.r11;
-	args->r12 = margs.r12;
-	args->r13 = margs.r13;
-	args->r14 = margs.r14;
-	args->r15 = margs.r15;
-	args->rdi = margs.rdi;
-	args->rsi = margs.rsi;
-	args->rbx = margs.rbx;
-	args->rdx = margs.rdx;
-
 	/* TDVMCALL leaf return code is in R10 */
 	return args->r10;
 }
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index aba58484ba10..125dda0b7827 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -46,7 +46,7 @@ void __tdx_hypercall_failed(void)
 long tdx_kvm_hypercall(unsigned int nr, unsigned long p1, unsigned long p2,
 		       unsigned long p3, unsigned long p4)
 {
-	struct tdx_hypercall_args args = {
+	struct tdx_module_args args = {
 		.r10 = nr,
 		.r11 = p1,
 		.r12 = p2,
@@ -106,7 +106,7 @@ EXPORT_SYMBOL_GPL(tdx_mcall_get_report0);
 
 static void __noreturn tdx_panic(const char *msg)
 {
-	struct tdx_hypercall_args args = {
+	struct tdx_module_args args = {
 		.r10 = TDX_HYPERCALL_STANDARD,
 		.r11 = TDVMCALL_REPORT_FATAL_ERROR,
 		.r12 = 0, /* Error code: 0 is Panic */
@@ -228,7 +228,7 @@ static int ve_instr_len(struct ve_info *ve)
 
 static u64 __cpuidle __halt(const bool irq_disabled)
 {
-	struct tdx_hypercall_args args = {
+	struct tdx_module_args args = {
 		.r10 = TDX_HYPERCALL_STANDARD,
 		.r11 = hcall_func(EXIT_REASON_HLT),
 		.r12 = irq_disabled,
@@ -272,7 +272,7 @@ void __cpuidle tdx_safe_halt(void)
 
 static int read_msr(struct pt_regs *regs, struct ve_info *ve)
 {
-	struct tdx_hypercall_args args = {
+	struct tdx_module_args args = {
 		.r10 = TDX_HYPERCALL_STANDARD,
 		.r11 = hcall_func(EXIT_REASON_MSR_READ),
 		.r12 = regs->cx,
@@ -293,7 +293,7 @@ static int read_msr(struct pt_regs *regs, struct ve_info *ve)
 
 static int write_msr(struct pt_regs *regs, struct ve_info *ve)
 {
-	struct tdx_hypercall_args args = {
+	struct tdx_module_args args = {
 		.r10 = TDX_HYPERCALL_STANDARD,
 		.r11 = hcall_func(EXIT_REASON_MSR_WRITE),
 		.r12 = regs->cx,
@@ -313,7 +313,7 @@ static int write_msr(struct pt_regs *regs, struct ve_info *ve)
 
 static int handle_cpuid(struct pt_regs *regs, struct ve_info *ve)
 {
-	struct tdx_hypercall_args args = {
+	struct tdx_module_args args = {
 		.r10 = TDX_HYPERCALL_STANDARD,
 		.r11 = hcall_func(EXIT_REASON_CPUID),
 		.r12 = regs->ax,
@@ -355,7 +355,7 @@ static int handle_cpuid(struct pt_regs *regs, struct ve_info *ve)
 
 static bool mmio_read(int size, unsigned long addr, unsigned long *val)
 {
-	struct tdx_hypercall_args args = {
+	struct tdx_module_args args = {
 		.r10 = TDX_HYPERCALL_STANDARD,
 		.r11 = hcall_func(EXIT_REASON_EPT_VIOLATION),
 		.r12 = size,
@@ -484,7 +484,7 @@ static int handle_mmio(struct pt_regs *regs, struct ve_info *ve)
 
 static bool handle_in(struct pt_regs *regs, int size, int port)
 {
-	struct tdx_hypercall_args args = {
+	struct tdx_module_args args = {
 		.r10 = TDX_HYPERCALL_STANDARD,
 		.r11 = hcall_func(EXIT_REASON_IO_INSTRUCTION),
 		.r12 = size,
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index 188e8bf3332c..74fc466dfdcd 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -83,29 +83,8 @@ u64 __tdcall(u64 fn, struct tdx_module_args *args);
 u64 __tdcall_ret(u64 fn, struct tdx_module_args *args);
 u64 __tdcall_saved_ret(u64 fn, struct tdx_module_args *args);
 
-/*
- * Used in __tdx_hypercall() to pass down and get back registers' values of
- * the TDCALL instruction when requesting services from the VMM.
- *
- * This is a software only structure and not part of the TDX module/VMM ABI.
- */
-struct tdx_hypercall_args {
-	u64 r8;
-	u64 r9;
-	u64 r10;
-	u64 r11;
-	u64 r12;
-	u64 r13;
-	u64 r14;
-	u64 r15;
-	u64 rdi;
-	u64 rsi;
-	u64 rbx;
-	u64 rdx;
-};
-
 /* Used to request services from the VMM */
-u64 __tdx_hypercall(struct tdx_hypercall_args *args);
+u64 __tdx_hypercall(struct tdx_module_args *args);
 
 /*
  * Wrapper for standard use of __tdx_hypercall with no output aside from
@@ -113,7 +92,7 @@ u64 __tdx_hypercall(struct tdx_hypercall_args *args);
  */
 static inline u64 _tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14, u64 r15)
 {
-	struct tdx_hypercall_args args = {
+	struct tdx_module_args args = {
 		.r10 = TDX_HYPERCALL_STANDARD,
 		.r11 = fn,
 		.r12 = r12,
-- 
2.41.0

[PATCH v2 10/11] x86/virt/tdx: Wire up basic SEAMCALL functions

[Kai Huang]

Intel Trust Domain Extensions (TDX) protects guest VMs from malicious
host and certain physical attacks.  A CPU-attested software module
called 'the TDX module' runs inside a new isolated memory range as a
trusted hypervisor to manage and run protected VMs.

TDX introduces a new CPU mode: Secure Arbitration Mode (SEAM).  This
mode runs only the TDX module itself or other code to load the TDX
module.

The host kernel communicates with SEAM software via a new SEAMCALL
instruction.  This is conceptually similar to a guest->host hypercall,
except it is made from the host to SEAM software instead.  The TDX
module establishes a new SEAMCALL ABI which allows the host to
initialize the module and to manage VMs.

The SEAMCALL ABI is very similar to the TDCALL ABI and leverages much
TDCALL infrastructure.  Wire up basic functions to make SEAMCALLs for
the TDX module initialization, which is the first step of TDX support.

To start to support TDX, create a new arch/x86/virt/vmx/tdx/tdx.c for
TDX host kernel support.  Add a new Kconfig option CONFIG_INTEL_TDX_HOST
to opt-in TDX host kernel support (to distinguish with TDX guest kernel
support).  So far only KVM uses TDX.  Make the new config option depend
on KVM_INTEL.

Signed-off-by: Kai Huang <kai.huang@intel.com>
---

v1 -> v2:
 - Removed __seamcall_saved_ret() and leave it to KVM TDX patches.

---
 arch/x86/Kconfig                 | 12 +++++++++
 arch/x86/Makefile                |  2 ++
 arch/x86/include/asm/tdx.h       |  6 +++++
 arch/x86/virt/Makefile           |  2 ++
 arch/x86/virt/vmx/Makefile       |  2 ++
 arch/x86/virt/vmx/tdx/Makefile   |  2 ++
 arch/x86/virt/vmx/tdx/seamcall.S | 42 ++++++++++++++++++++++++++++++++
 7 files changed, 68 insertions(+)
 create mode 100644 arch/x86/virt/Makefile
 create mode 100644 arch/x86/virt/vmx/Makefile
 create mode 100644 arch/x86/virt/vmx/tdx/Makefile
 create mode 100644 arch/x86/virt/vmx/tdx/seamcall.S

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 7422db409770..0558dd98abd7 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1949,6 +1949,18 @@ config X86_SGX
 
 	  If unsure, say N.
 
+config INTEL_TDX_HOST
+	bool "Intel Trust Domain Extensions (TDX) host support"
+	depends on CPU_SUP_INTEL
+	depends on X86_64
+	depends on KVM_INTEL
+	help
+	  Intel Trust Domain Extensions (TDX) protects guest VMs from malicious
+	  host and certain physical attacks.  This option enables necessary TDX
+	  support in the host kernel to run confidential VMs.
+
+	  If unsure, say N.
+
 config EFI
 	bool "EFI runtime service support"
 	depends on ACPI
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index fdc2e3abd615..5d8d1892aae9 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -252,6 +252,8 @@ archheaders:
 
 libs-y  += arch/x86/lib/
 
+core-y += arch/x86/virt/
+
 # drivers-y are linked after core-y
 drivers-$(CONFIG_MATH_EMULATION) += arch/x86/math-emu/
 drivers-$(CONFIG_PCI)            += arch/x86/pci/
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 603e6d1e9d4a..942edc8e9ba8 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -72,5 +72,11 @@ static inline long tdx_kvm_hypercall(unsigned int nr, unsigned long p1,
 	return -ENODEV;
 }
 #endif /* CONFIG_INTEL_TDX_GUEST && CONFIG_KVM_GUEST */
+
+#ifdef CONFIG_INTEL_TDX_HOST
+u64 __seamcall(u64 fn, struct tdx_module_args *args);
+u64 __seamcall_ret(u64 fn, struct tdx_module_args *args);
+#endif	/* CONFIG_INTEL_TDX_HOST */
+
 #endif /* !__ASSEMBLY__ */
 #endif /* _ASM_X86_TDX_H */
diff --git a/arch/x86/virt/Makefile b/arch/x86/virt/Makefile
new file mode 100644
index 000000000000..1e36502cd738
--- /dev/null
+++ b/arch/x86/virt/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-y	+= vmx/
diff --git a/arch/x86/virt/vmx/Makefile b/arch/x86/virt/vmx/Makefile
new file mode 100644
index 000000000000..feebda21d793
--- /dev/null
+++ b/arch/x86/virt/vmx/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_INTEL_TDX_HOST)	+= tdx/
diff --git a/arch/x86/virt/vmx/tdx/Makefile b/arch/x86/virt/vmx/tdx/Makefile
new file mode 100644
index 000000000000..46ef8f73aebb
--- /dev/null
+++ b/arch/x86/virt/vmx/tdx/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-y += seamcall.o
diff --git a/arch/x86/virt/vmx/tdx/seamcall.S b/arch/x86/virt/vmx/tdx/seamcall.S
new file mode 100644
index 000000000000..b32934837f16
--- /dev/null
+++ b/arch/x86/virt/vmx/tdx/seamcall.S
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/linkage.h>
+#include <asm/frame.h>
+
+#include "tdxcall.S"
+
+/*
+ * __seamcall() - Host-side interface functions to SEAM software
+ * (the P-SEAMLDR or the TDX module).
+ *
+ * __seamcall() function ABI:
+ *
+ * @fn   (RDI)  - SEAMCALL Leaf number, moved to RAX
+ * @args (RSI)  - struct tdx_module_args for input
+ *
+ * Only RCX/RDX/R8-R11 are used as input registers.
+ *
+ * Return (via RAX) TDX_SEAMCALL_VMFAILINVALID if the SEAMCALL itself
+ * fails, or the completion status of the SEAMCALL leaf function.
+ */
+SYM_FUNC_START(__seamcall)
+	TDX_MODULE_CALL host=1
+SYM_FUNC_END(__seamcall)
+
+/*
+ * __seamcall_ret() - Host-side interface functions to SEAM software
+ * (the P-SEAMLDR or the TDX module), with saving RCX/RDX/R8-R11
+ * output registers to the 'struct tdx_module_args' used as input.
+ *
+ * __seamcall_ret() function ABI:
+ *
+ * @fn   (RDI)  - SEAMCALL Leaf number, moved to RAX
+ * @args (RSI)  - struct tdx_module_args for input and output
+ *
+ * Only RCX/RDX/R8-R11 are used as input/output registers.
+ *
+ * Return (via RAX) TDX_SEAMCALL_VMFAILINVALID if the SEAMCALL itself
+ * fails, or the completion status of the SEAMCALL leaf function.
+ */
+SYM_FUNC_START(__seamcall_ret)
+	TDX_MODULE_CALL host=1 ret=1
+SYM_FUNC_END(__seamcall_ret)
-- 
2.41.0

[PATCH v2 11/11] x86/virt/tdx: Allow SEAMCALL to handle #UD and #GP

[Kai Huang]

On the platform with the "partial write machine check" erratum, a kernel
partial write to TDX private memory may cause unexpected machine check.
It would be nice if the #MC handler could print additional information
to show the #MC was TDX private memory error due to possible kernel bug.

To do that, the machine check handler needs to use SEAMCALL to query
page type of the error memory from the TDX module, because there's no
existing infrastructure to track TDX private pages.

SEAMCALL instruction causes #UD if CPU isn't in VMX operation.  In #MC
handler, it is legal that CPU isn't in VMX operation when making this
SEAMCALL.  Extend the TDX_MODULE_CALL macro to handle #UD so the
SEAMCALL can return error code instead of Oops in the #MC handler.
Opportunistically handles #GP too since they share the same code.

A bonus is when kernel mistakenly calls SEAMCALL when CPU isn't in VMX
operation, or when TDX isn't enabled by the BIOS, or when the BIOS is
buggy, the kernel can get a nicer error message rather than a less
understandable Oops.

This is basically based on Peter's code.

Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kai Huang <kai.huang@intel.com>
---

v1 -> v2:
 - Skip saving output registers when SEAMCALL #UD/#GP

---
 arch/x86/include/asm/tdx.h      |  4 ++++
 arch/x86/virt/vmx/tdx/tdxcall.S | 19 +++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 942edc8e9ba8..a51ca2bcd289 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -8,6 +8,7 @@
 
 #include <asm/errno.h>
 #include <asm/ptrace.h>
+#include <asm/trapnr.h>
 #include <asm/shared/tdx.h>
 
 /*
@@ -20,6 +21,9 @@
 #define TDX_SW_ERROR			(TDX_ERROR | GENMASK_ULL(47, 40))
 #define TDX_SEAMCALL_VMFAILINVALID	(TDX_SW_ERROR | _UL(0xFFFF0000))
 
+#define TDX_SEAMCALL_GP			(TDX_SW_ERROR | X86_TRAP_GP)
+#define TDX_SEAMCALL_UD			(TDX_SW_ERROR | X86_TRAP_UD)
+
 #ifndef __ASSEMBLY__
 
 /*
diff --git a/arch/x86/virt/vmx/tdx/tdxcall.S b/arch/x86/virt/vmx/tdx/tdxcall.S
index 3ed6d8b8d2a9..0eface625b59 100644
--- a/arch/x86/virt/vmx/tdx/tdxcall.S
+++ b/arch/x86/virt/vmx/tdx/tdxcall.S
@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 #include <asm/asm-offsets.h>
 #include <asm/frame.h>
+#include <asm/asm.h>
 #include <asm/tdx.h>
 
 /*
@@ -85,6 +86,7 @@
 .endif	/* \saved */
 
 .if \host
+.Lseamcall\@:
 	seamcall
 	/*
 	 * SEAMCALL instruction is essentially a VMExit from VMX root
@@ -192,11 +194,28 @@
 .if \host
 .Lseamcall_vmfailinvalid\@:
 	mov $TDX_SEAMCALL_VMFAILINVALID, %rax
+	jmp .Lseamcall_fail\@
+
+.Lseamcall_trap\@:
+	/*
+	 * SEAMCALL caused #GP or #UD.  By reaching here %eax contains
+	 * the trap number.  Convert the trap number to the TDX error
+	 * code by setting TDX_SW_ERROR to the high 32-bits of %rax.
+	 *
+	 * Note cannot OR TDX_SW_ERROR directly to %rax as OR instruction
+	 * only accepts 32-bit immediate at most.
+	 */
+	movq $TDX_SW_ERROR, %r12
+	orq  %r12, %rax
+
+.Lseamcall_fail\@:
 .if \ret && \saved
 	/* pop the unused structure pointer back to %rsi */
 	popq %rsi
 .endif
 	jmp .Lout\@
+
+	_ASM_EXTABLE_FAULT(.Lseamcall\@, .Lseamcall_trap\@)
 .endif	/* \host */
 
 .endm
-- 
2.41.0

Re: [PATCH v2 00/11] Unify TDCALL/SEAMCALL and TDVMCALL assembly

[Peter Zijlstra]

On Fri, Jul 21, 2023 at 12:28:03AM +1200, Kai Huang wrote:

> Kai Huang (11):
>   x86/tdx: Zero out the missing RSI in TDX_HYPERCALL macro
>   x86/tdx: Skip saving output regs when SEAMCALL fails with
>     VMFailInvalid
>   x86/tdx: Make macros of TDCALLs consistent with the spec
>   x86/tdx: Rename __tdx_module_call() to __tdcall()
>   x86/tdx: Pass TDCALL/SEAMCALL input/output registers via a structure
>   x86/tdx: Extend TDX_MODULE_CALL to support more TDCALL/SEAMCALL leafs
>   x86/tdx: Make TDX_HYPERCALL asm similar to TDX_MODULE_CALL
>   x86/tdx: Reimplement __tdx_hypercall() using TDX_MODULE_CALL asm
>   x86/tdx: Remove 'struct tdx_hypercall_args'
>   x86/virt/tdx: Wire up basic SEAMCALL functions
>   x86/virt/tdx: Allow SEAMCALL to handle #UD and #GP

These look ok to me, thanks!

This does not yet re-order the args structure to conform to the hardware
index order as per kvm's requirement, right? That will be part of the
KVM series?

Re: [PATCH v2 00/11] Unify TDCALL/SEAMCALL and TDVMCALL assembly

[Huang, Kai]

On Thu, 2023-07-20 at 15:16 +0200, Peter Zijlstra wrote:
> On Fri, Jul 21, 2023 at 12:28:03AM +1200, Kai Huang wrote:
> 
> > Kai Huang (11):
> >   x86/tdx: Zero out the missing RSI in TDX_HYPERCALL macro
> >   x86/tdx: Skip saving output regs when SEAMCALL fails with
> >     VMFailInvalid
> >   x86/tdx: Make macros of TDCALLs consistent with the spec
> >   x86/tdx: Rename __tdx_module_call() to __tdcall()
> >   x86/tdx: Pass TDCALL/SEAMCALL input/output registers via a structure
> >   x86/tdx: Extend TDX_MODULE_CALL to support more TDCALL/SEAMCALL leafs
> >   x86/tdx: Make TDX_HYPERCALL asm similar to TDX_MODULE_CALL
> >   x86/tdx: Reimplement __tdx_hypercall() using TDX_MODULE_CALL asm
> >   x86/tdx: Remove 'struct tdx_hypercall_args'
> >   x86/virt/tdx: Wire up basic SEAMCALL functions
> >   x86/virt/tdx: Allow SEAMCALL to handle #UD and #GP
> 
> These look ok to me, thanks!

Thanks!

> 
> This does not yet re-order the args structure to conform to the hardware
> index order as per kvm's requirement, right? That will be part of the
> KVM series?

Unfortunately I don't think it's feasible.  Sean pointed out that
kvm_vcpu_arch::regs[] do follow the "register index" hardware layout in x86 (for
which I missed sorry), so we cannot re-order KVM part.  

And unfortunately RBP (5) is in middle of those registers:

	0 = RAX
	1 = RCX
	2 = RDX
	3 = RBX
	4 = RSP
	5 = RBP
	6 = RSI
	7 = RDI
	8–15 represent R8–R15, respectively...

Thus unless we add RBP to 'struct tdx_module_args', it's impossible to re-order
the structure to match KVM's layout.

Re: [PATCH v2 07/11] x86/tdx: Make TDX_HYPERCALL asm similar to TDX_MODULE_CALL

[Huang, Kai]

> 
> With above changes, change the asm function from __tdx_hypercall() to
> __tdcall_hypercall(), and reimplement __tdx_hypercall() as the C wrapper
> of it.  This avoids having to add another wrapper of __tdx_hypercall()
> (_tdx_hypercall() is already taken).
> 
[...]
> 
> By changing __tdx_hypercall() to a C function, __tdx_hypercall_failed()
> is no longer called from '.noinstr.text', thus remove the 'noinstr'
> annotation and the 'instrumentation_begin()'.
> 

Hi Peter,

Sorry I got a build regression from lkp:

vmlinux.o: warning: objtool: __halt+0x3a: call to __tdx_hypercall() leaves
.noinstr.text section

The reason is __halt() is annotated with "__cpuidle", but it calls
__tdx_hypercall(), which is now a normal C function, w/o
instrumentation_begin()/end().

I think we can annotate __tdx_hypercall() as 'noinstr' too and keep
__tdx_hypercall_failed() unchanged.  Anyway in the upstream code,
__tdx_hypercall() is in '.noinstr.text'.

diff --git a/arch/x86/coco/tdx/tdx-shared.c b/arch/x86/coco/tdx/tdx-shared.c
index 13139ee171c8..b47c8cce91b0 100644
--- a/arch/x86/coco/tdx/tdx-shared.c
+++ b/arch/x86/coco/tdx/tdx-shared.c
@@ -70,7 +70,7 @@ bool tdx_accept_memory(phys_addr_t start, phys_addr_t end)
        return true;
 }
 
-u64 __tdx_hypercall(struct tdx_hypercall_args *args)
+noinstr u64 __tdx_hypercall(struct tdx_hypercall_args *args)
 {
        struct tdx_module_args margs = {
                .rcx = TDVMCALL_EXPOSE_REGS_MASK,
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index aba58484ba10..f10b0e512a36 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -37,8 +37,9 @@
 
 #define TDREPORT_SUBTYPE_0     0
 
-void __tdx_hypercall_failed(void)
+noinstr void __tdx_hypercall_failed(void)
 {
+       instrumentation_begin();
        panic("TDVMCALL failed. TDX module bug?");
 }


We can fold this to this patch.

Do you have any comments?

Re: [PATCH v2 07/11] x86/tdx: Make TDX_HYPERCALL asm similar to TDX_MODULE_CALL

[Peter Zijlstra]

On Fri, Jul 21, 2023 at 05:19:30AM +0000, Huang, Kai wrote:

> Sorry I got a build regression from lkp:
> 
> vmlinux.o: warning: objtool: __halt+0x3a: call to __tdx_hypercall() leaves
> .noinstr.text section

Clearly you should enable CONFIG_DEBUG_ENTRY in your own development
.config ;-)

> The reason is __halt() is annotated with "__cpuidle", but it calls
> __tdx_hypercall(), which is now a normal C function, w/o
> instrumentation_begin()/end().
> 
> I think we can annotate __tdx_hypercall() as 'noinstr' too and keep
> __tdx_hypercall_failed() unchanged.  Anyway in the upstream code,
> __tdx_hypercall() is in '.noinstr.text'.
> 
> diff --git a/arch/x86/coco/tdx/tdx-shared.c b/arch/x86/coco/tdx/tdx-shared.c
> index 13139ee171c8..b47c8cce91b0 100644
> --- a/arch/x86/coco/tdx/tdx-shared.c
> +++ b/arch/x86/coco/tdx/tdx-shared.c
> @@ -70,7 +70,7 @@ bool tdx_accept_memory(phys_addr_t start, phys_addr_t end)
>         return true;
>  }
>  
> -u64 __tdx_hypercall(struct tdx_hypercall_args *args)
> +noinstr u64 __tdx_hypercall(struct tdx_hypercall_args *args)
>  {
>         struct tdx_module_args margs = {
>                 .rcx = TDVMCALL_EXPOSE_REGS_MASK,
> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index aba58484ba10..f10b0e512a36 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -37,8 +37,9 @@
>  
>  #define TDREPORT_SUBTYPE_0     0
>  
> -void __tdx_hypercall_failed(void)
> +noinstr void __tdx_hypercall_failed(void)
>  {
> +       instrumentation_begin();
>         panic("TDVMCALL failed. TDX module bug?");
>  }
> 
> 
> We can fold this to this patch.
> 
> Do you have any comments?

Yes this is fine, we violate noinstr for WARN etc.. There's no point
being pendantic about these things if we're going to take the machine
down anyway.

Re: [PATCH v2 00/11] Unify TDCALL/SEAMCALL and TDVMCALL assembly

[Peter Zijlstra]

On Fri, Jul 21, 2023 at 12:18:23AM +0000, Huang, Kai wrote:

> Unfortunately I don't think it's feasible.  Sean pointed out that
> kvm_vcpu_arch::regs[] do follow the "register index" hardware layout in x86 (for
> which I missed sorry), so we cannot re-order KVM part.  
> 
> And unfortunately RBP (5) is in middle of those registers:
> 
> 	0 = RAX
> 	1 = RCX
> 	2 = RDX
> 	3 = RBX
> 	4 = RSP
> 	5 = RBP
> 	6 = RSI
> 	7 = RDI
> 	8–15 represent R8–R15, respectively...
> 
> Thus unless we add RBP to 'struct tdx_module_args', it's impossible to re-order
> the structure to match KVM's layout.

Adding RBP to the struct shouldn't be a problem, we'll just not use it.
Same as RSP, nobody sane would expect that to be used. If you worry
about it you can give them funny names like:

struct tdx_module_args {
	unsigned long ax;
	unsigned long cx;
	unsigned long dx;
	unsigned long bx;
	unsigned long __sp_unused;
	unsigned long __bp_unused;
	unsigned long si;
	unsigned long di;
	...
};

I mean, at this point the whole thing is just 128 bytes of data anyway.

Re: [PATCH v2 00/11] Unify TDCALL/SEAMCALL and TDVMCALL assembly

[Huang, Kai]

On Fri, 2023-07-21 at 10:06 +0200, Peter Zijlstra wrote:
> On Fri, Jul 21, 2023 at 12:18:23AM +0000, Huang, Kai wrote:
> 
> > Unfortunately I don't think it's feasible.  Sean pointed out that
> > kvm_vcpu_arch::regs[] do follow the "register index" hardware layout in x86 (for
> > which I missed sorry), so we cannot re-order KVM part.  
> > 
> > And unfortunately RBP (5) is in middle of those registers:
> > 
> > 	0 = RAX
> > 	1 = RCX
> > 	2 = RDX
> > 	3 = RBX
> > 	4 = RSP
> > 	5 = RBP
> > 	6 = RSI
> > 	7 = RDI
> > 	8–15 represent R8–R15, respectively...
> > 
> > Thus unless we add RBP to 'struct tdx_module_args', it's impossible to re-order
> > the structure to match KVM's layout.
> 
> Adding RBP to the struct shouldn't be a problem, we'll just not use it.
> Same as RSP, nobody sane would expect that to be used. If you worry
> about it you can give them funny names like:
> 
> struct tdx_module_args {
> 	unsigned long ax;
> 	unsigned long cx;
> 	unsigned long dx;
> 	unsigned long bx;
> 	unsigned long __sp_unused;
> 	unsigned long __bp_unused;
> 	unsigned long si;
> 	unsigned long di;
> 	...
> };
> 
> I mean, at this point the whole thing is just 128 bytes of data anyway.

Sure I can do.

How about adding an additional patch on top of this series?  

For instance, below patch (compile only):

From c63d01bf91fe23f1e2d2e085644326bdee114d49 Mon Sep 17 00:00:00 2001
From: Kai Huang <kai.huang@intel.com>
Date: Fri, 21 Jul 2023 22:06:31 +1200
Subject: [PATCH] x86/tdx: Add __seamcall_saved_ret() for TDH.VP.ENTER

For TDX guest, KVM uses TDH.VP.ENTER SEAMCALL leaf to enter the guest.
When TDH.VP.ENTER returns to KVM due to TDG.VP.VMCALL from the TDX
guest, all RCX/RDX/RBX/RDI/RSI/R8-R15 are valid output registers, and
the following TDH.VP.ENTER also uses all those registers as input.

Introduce __seamcall_saved_ret(), which uses all above registers as
both input/output, for KVM to support TDH.VP.ENTER.

Also, KVM caches guest's GPRs in 'kvm_vcpu_arch::regs[]', which follows
follows the "register index" hardware layout of x86 GPRs.  However the
__seamcall_saved_ret() takes the pointer of 'struct tdx_module_args' as
argument, thus there's a mismatch here.

One option is KVM to copy input registers from 'vcpu::regs[]' to a
'struct tdx_module_args' on the stack and use that to make the SEAMCALL,
but such memory copy isn't desired and should be avoided if possible.
It's not feasible to change KVM's 'vcpu::regs[]' layout due to various
reasons (e.g., emulation code uses decoded register index as array index
to access the register).  Therefore, adjust 'struct tdx_module_args' to
match KVM's 'vcpu::regs[]' so that KVM can simply do below:

        seamcall_saved_ret(TDH.VP.ENTER,
                        (struct tdx_module_args *)vcpu->arch->regs);

Note RAX/RSP/RBP are not used by the TDX_MODULE_CALL assembly, but they
are necessary in order match the layout of 'struct tdx_module_args' to
KVM's 'vcpu::regs[]'.  Thus add them to the structure, but name them as
*_unused.  Also don't include them to asm-offset.c so that any misuse of
them in the assembly would result in build error.

Signed-off-by: Kai Huang <kai.huang@intel.com>
---
 arch/x86/include/asm/shared/tdx.h | 19 +++++++++++++------
 arch/x86/virt/vmx/tdx/seamcall.S  | 19 +++++++++++++++++++
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/shared/tdx.h
b/arch/x86/include/asm/shared/tdx.h
index 74fc466dfdcd..8d1427562c63 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -58,24 +58,31 @@
  * Used in __tdcall*() to gather the input/output registers' values of the
  * TDCALL instruction when requesting services from the TDX module. This is a
  * software only structure and not part of the TDX module/VMM ABI
+ *
+ * Note those *_unused are not used by the TDX_MODULE_CALL assembly.
+ * The layout of this structure also matches KVM's kvm_vcpu_arch::regs[]
+ * layout, which follows the "register index" order of x86 GPRs.  KVM
+ * then can simply type cast kvm_vcpu_arch::regs[] to this structure to
+ * avoid the extra memory copy between two structures when making
+ * TDH.VP.ENTER SEAMCALL.
  */
 struct tdx_module_args {
-       /* callee-clobbered */
+       u64 rax_unused;
        u64 rcx;
        u64 rdx;
+       u64 rbx;
+       u64 rsp_unused;
+       u64 rbp_unused;
+       u64 rsi;
+       u64 rdi;
        u64 r8;
        u64 r9;
-       /* extra callee-clobbered */
        u64 r10;
        u64 r11;
-       /* callee-saved + rdi/rsi */
        u64 r12;
        u64 r13;
        u64 r14;
        u64 r15;
-       u64 rbx;
-       u64 rdi;
-       u64 rsi;
 }; 

/* Used to communicate with the TDX module */
diff --git a/arch/x86/virt/vmx/tdx/seamcall.S b/arch/x86/virt/vmx/tdx/seamcall.S
index b32934837f16..f251ebadb014 100644
--- a/arch/x86/virt/vmx/tdx/seamcall.S
+++ b/arch/x86/virt/vmx/tdx/seamcall.S
@@ -40,3 +40,22 @@ SYM_FUNC_END(__seamcall)
 SYM_FUNC_START(__seamcall_ret)
        TDX_MODULE_CALL host=1 ret=1
 SYM_FUNC_END(__seamcall_ret)
+
+/*
+ * __seamcall_saved_ret() - Host-side interface functions to SEAM software
+ * (the P-SEAMLDR or the TDX module), with saving output registers to the
+ * 'struct tdx_module_args' used as input.
+ *
+ * __seamcall_saved_ret() function ABI:
+ *
+ * @fn   (RDI)  - SEAMCALL Leaf number, moved to RAX
+ * @args (RSI)  - struct tdx_module_args for input and output
+ *
+ * All registers in @args are used as input/output registers.
+ *
+ * Return (via RAX) TDX_SEAMCALL_VMFAILINVALID if the SEAMCALL itself
+ * fails, or the completion status of the SEAMCALL leaf function.
+ */
+SYM_FUNC_START(__seamcall_ret)
+       TDX_MODULE_CALL host=1 ret=1 saved=1
+SYM_FUNC_END(__seamcall_ret)
-- 
2.41.0

Re: [PATCH v2 07/11] x86/tdx: Make TDX_HYPERCALL asm similar to TDX_MODULE_CALL

[Huang, Kai]

On Fri, 2023-07-21 at 10:01 +0200, Peter Zijlstra wrote:
> On Fri, Jul 21, 2023 at 05:19:30AM +0000, Huang, Kai wrote:
> 
> > Sorry I got a build regression from lkp:
> > 
> > vmlinux.o: warning: objtool: __halt+0x3a: call to __tdx_hypercall() leaves
> > .noinstr.text section
> 
> Clearly you should enable CONFIG_DEBUG_ENTRY in your own development
> .config ;-)

Ah thanks a lot!

I've been investigating how to reproduce at my own environment this afternoon!

LKP people are not aware of what triggered this check either.  I'll pass to
them.

> 
> > The reason is __halt() is annotated with "__cpuidle", but it calls
> > __tdx_hypercall(), which is now a normal C function, w/o
> > instrumentation_begin()/end().
> > 
> > I think we can annotate __tdx_hypercall() as 'noinstr' too and keep
> > __tdx_hypercall_failed() unchanged.  Anyway in the upstream code,
> > __tdx_hypercall() is in '.noinstr.text'.
> > 
> > diff --git a/arch/x86/coco/tdx/tdx-shared.c b/arch/x86/coco/tdx/tdx-shared.c
> > index 13139ee171c8..b47c8cce91b0 100644
> > --- a/arch/x86/coco/tdx/tdx-shared.c
> > +++ b/arch/x86/coco/tdx/tdx-shared.c
> > @@ -70,7 +70,7 @@ bool tdx_accept_memory(phys_addr_t start, phys_addr_t end)
> >         return true;
> >  }
> >  
> > -u64 __tdx_hypercall(struct tdx_hypercall_args *args)
> > +noinstr u64 __tdx_hypercall(struct tdx_hypercall_args *args)
> >  {
> >         struct tdx_module_args margs = {
> >                 .rcx = TDVMCALL_EXPOSE_REGS_MASK,
> > diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> > index aba58484ba10..f10b0e512a36 100644
> > --- a/arch/x86/coco/tdx/tdx.c
> > +++ b/arch/x86/coco/tdx/tdx.c
> > @@ -37,8 +37,9 @@
> >  
> >  #define TDREPORT_SUBTYPE_0     0
> >  
> > -void __tdx_hypercall_failed(void)
> > +noinstr void __tdx_hypercall_failed(void)
> >  {
> > +       instrumentation_begin();
> >         panic("TDVMCALL failed. TDX module bug?");
> >  }
> > 
> > 
> > We can fold this to this patch.
> > 
> > Do you have any comments?
> 
> Yes this is fine, we violate noinstr for WARN etc.. There's no point
> being pendantic about these things if we're going to take the machine
> down anyway.

Thanks.  I'll fold above to this patch and sent out a v3 (given that it seems
you also want a patch to adjust the layout of 'struct tdx_module_args' for
TDH.VP.ENTER).

Re: [PATCH v2 00/11] Unify TDCALL/SEAMCALL and TDVMCALL assembly

[Huang, Kai]

On Fri, 2023-07-21 at 11:02 +0000, Huang, Kai wrote:
> On Fri, 2023-07-21 at 10:06 +0200, Peter Zijlstra wrote:
> > On Fri, Jul 21, 2023 at 12:18:23AM +0000, Huang, Kai wrote:
> > 
> > > Unfortunately I don't think it's feasible.  Sean pointed out that
> > > kvm_vcpu_arch::regs[] do follow the "register index" hardware layout in x86 (for
> > > which I missed sorry), so we cannot re-order KVM part.  
> > > 
> > > And unfortunately RBP (5) is in middle of those registers:
> > > 
> > > 	0 = RAX
> > > 	1 = RCX
> > > 	2 = RDX
> > > 	3 = RBX
> > > 	4 = RSP
> > > 	5 = RBP
> > > 	6 = RSI
> > > 	7 = RDI
> > > 	8–15 represent R8–R15, respectively...
> > > 
> > > Thus unless we add RBP to 'struct tdx_module_args', it's impossible to re-order
> > > the structure to match KVM's layout.
> > 
> > Adding RBP to the struct shouldn't be a problem, we'll just not use it.
> > Same as RSP, nobody sane would expect that to be used. If you worry
> > about it you can give them funny names like:
> > 
> > struct tdx_module_args {
> > 	unsigned long ax;
> > 	unsigned long cx;
> > 	unsigned long dx;
> > 	unsigned long bx;
> > 	unsigned long __sp_unused;
> > 	unsigned long __bp_unused;
> > 	unsigned long si;
> > 	unsigned long di;
> > 	...
> > };
> > 
> > I mean, at this point the whole thing is just 128 bytes of data anyway.
> 
> Sure I can do.
> 
> How about adding an additional patch on top of this series?  
> 
> For instance, below patch (compile only):
> 
> From c63d01bf91fe23f1e2d2e085644326bdee114d49 Mon Sep 17 00:00:00 2001
> From: Kai Huang <kai.huang@intel.com>
> Date: Fri, 21 Jul 2023 22:06:31 +1200
> Subject: [PATCH] x86/tdx: Add __seamcall_saved_ret() for TDH.VP.ENTER
> 
> For TDX guest, KVM uses TDH.VP.ENTER SEAMCALL leaf to enter the guest.
> When TDH.VP.ENTER returns to KVM due to TDG.VP.VMCALL from the TDX
> guest, all RCX/RDX/RBX/RDI/RSI/R8-R15 are valid output registers, and
> the following TDH.VP.ENTER also uses all those registers as input.
> 
> Introduce __seamcall_saved_ret(), which uses all above registers as
> both input/output, for KVM to support TDH.VP.ENTER.
> 
> Also, KVM caches guest's GPRs in 'kvm_vcpu_arch::regs[]', which follows
> follows the "register index" hardware layout of x86 GPRs.  However the
> __seamcall_saved_ret() takes the pointer of 'struct tdx_module_args' as
> argument, thus there's a mismatch here.
> 
> One option is KVM to copy input registers from 'vcpu::regs[]' to a
> 'struct tdx_module_args' on the stack and use that to make the SEAMCALL,
> but such memory copy isn't desired and should be avoided if possible.
> It's not feasible to change KVM's 'vcpu::regs[]' layout due to various
> reasons (e.g., emulation code uses decoded register index as array index
> to access the register).  Therefore, adjust 'struct tdx_module_args' to
> match KVM's 'vcpu::regs[]' so that KVM can simply do below:
> 
>         seamcall_saved_ret(TDH.VP.ENTER,
>                         (struct tdx_module_args *)vcpu->arch->regs);
> 
> Note RAX/RSP/RBP are not used by the TDX_MODULE_CALL assembly, but they
> are necessary in order match the layout of 'struct tdx_module_args' to
> KVM's 'vcpu::regs[]'.  Thus add them to the structure, but name them as
> *_unused.  Also don't include them to asm-offset.c so that any misuse of
> them in the assembly would result in build error.
> 
> Signed-off-by: Kai Huang <kai.huang@intel.com>
> ---
>  arch/x86/include/asm/shared/tdx.h | 19 +++++++++++++------
>  arch/x86/virt/vmx/tdx/seamcall.S  | 19 +++++++++++++++++++
>  2 files changed, 32 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/include/asm/shared/tdx.h
> b/arch/x86/include/asm/shared/tdx.h
> index 74fc466dfdcd..8d1427562c63 100644
> --- a/arch/x86/include/asm/shared/tdx.h
> +++ b/arch/x86/include/asm/shared/tdx.h
> @@ -58,24 +58,31 @@
>   * Used in __tdcall*() to gather the input/output registers' values of the
>   * TDCALL instruction when requesting services from the TDX module. This is a
>   * software only structure and not part of the TDX module/VMM ABI
> + *
> + * Note those *_unused are not used by the TDX_MODULE_CALL assembly.
> + * The layout of this structure also matches KVM's kvm_vcpu_arch::regs[]
> + * layout, which follows the "register index" order of x86 GPRs.  KVM
> + * then can simply type cast kvm_vcpu_arch::regs[] to this structure to
> + * avoid the extra memory copy between two structures when making
> + * TDH.VP.ENTER SEAMCALL.
>   */
>  struct tdx_module_args {
> -       /* callee-clobbered */
> +       u64 rax_unused;
>         u64 rcx;
>         u64 rdx;
> +       u64 rbx;
> +       u64 rsp_unused;
> +       u64 rbp_unused;
> +       u64 rsi;
> +       u64 rdi;
>         u64 r8;
>         u64 r9;
> -       /* extra callee-clobbered */
>         u64 r10;
>         u64 r11;
> -       /* callee-saved + rdi/rsi */
>         u64 r12;
>         u64 r13;
>         u64 r14;
>         u64 r15;
> -       u64 rbx;
> -       u64 rdi;
> -       u64 rsi;
>  }; 
> 
> /* Used to communicate with the TDX module */
> diff --git a/arch/x86/virt/vmx/tdx/seamcall.S b/arch/x86/virt/vmx/tdx/seamcall.S
> index b32934837f16..f251ebadb014 100644
> --- a/arch/x86/virt/vmx/tdx/seamcall.S
> +++ b/arch/x86/virt/vmx/tdx/seamcall.S
> @@ -40,3 +40,22 @@ SYM_FUNC_END(__seamcall)
>  SYM_FUNC_START(__seamcall_ret)
>         TDX_MODULE_CALL host=1 ret=1
>  SYM_FUNC_END(__seamcall_ret)
> +
> +/*
> + * __seamcall_saved_ret() - Host-side interface functions to SEAM software
> + * (the P-SEAMLDR or the TDX module), with saving output registers to the
> + * 'struct tdx_module_args' used as input.
> + *
> + * __seamcall_saved_ret() function ABI:
> + *
> + * @fn   (RDI)  - SEAMCALL Leaf number, moved to RAX
> + * @args (RSI)  - struct tdx_module_args for input and output
> + *
> + * All registers in @args are used as input/output registers.
> + *
> + * Return (via RAX) TDX_SEAMCALL_VMFAILINVALID if the SEAMCALL itself
> + * fails, or the completion status of the SEAMCALL leaf function.
> + */
> +SYM_FUNC_START(__seamcall_ret)
> +       TDX_MODULE_CALL host=1 ret=1 saved=1
> +SYM_FUNC_END(__seamcall_ret)

Sorry should be __seamcall_saved_ret.

> -- 
> 2.41.0
> 
> 

Sorry missing the declaration of __seamcall_saved_ret():

--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -80,6 +80,7 @@ static inline long tdx_kvm_hypercall(unsigned int nr, unsigned
long p1,
 #ifdef CONFIG_INTEL_TDX_HOST
 u64 __seamcall(u64 fn, struct tdx_module_args *args);
 u64 __seamcall_ret(u64 fn, struct tdx_module_args *args);
+u64 __seamcall_saved_ret(u64 fn, struct tdx_module_args *args);

And perhaps we should adjust the order of registers in asm-offset.c to match the
change to the 'struct tdx_module_args'?

--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -70,6 +70,9 @@ static void __used common(void)
        BLANK();
        OFFSET(TDX_MODULE_rcx, tdx_module_args, rcx);
        OFFSET(TDX_MODULE_rdx, tdx_module_args, rdx);
+       OFFSET(TDX_MODULE_rbx, tdx_module_args, rbx);
+       OFFSET(TDX_MODULE_rsi, tdx_module_args, rsi);
+       OFFSET(TDX_MODULE_rdi, tdx_module_args, rdi);
        OFFSET(TDX_MODULE_r8,  tdx_module_args, r8);
        OFFSET(TDX_MODULE_r9,  tdx_module_args, r9);
        OFFSET(TDX_MODULE_r10, tdx_module_args, r10);
@@ -78,9 +81,6 @@ static void __used common(void)
        OFFSET(TDX_MODULE_r13, tdx_module_args, r13);
        OFFSET(TDX_MODULE_r14, tdx_module_args, r14);
        OFFSET(TDX_MODULE_r15, tdx_module_args, r15);
-       OFFSET(TDX_MODULE_rbx, tdx_module_args, rbx);
-       OFFSET(TDX_MODULE_rdi, tdx_module_args, rdi);
-       OFFSET(TDX_MODULE_rsi, tdx_module_args, rsi);

Re: [PATCH v2 00/11] Unify TDCALL/SEAMCALL and TDVMCALL assembly

[Huang, Kai]

On Fri, 2023-07-21 at 11:44 +0000, Huang, Kai wrote:
> On Fri, 2023-07-21 at 11:02 +0000, Huang, Kai wrote:
> > On Fri, 2023-07-21 at 10:06 +0200, Peter Zijlstra wrote:
> > > On Fri, Jul 21, 2023 at 12:18:23AM +0000, Huang, Kai wrote:
> > > 
> > > > Unfortunately I don't think it's feasible.  Sean pointed out that
> > > > kvm_vcpu_arch::regs[] do follow the "register index" hardware layout in x86 (for
> > > > which I missed sorry), so we cannot re-order KVM part.  
> > > > 
> > > > And unfortunately RBP (5) is in middle of those registers:
> > > > 
> > > > 	0 = RAX
> > > > 	1 = RCX
> > > > 	2 = RDX
> > > > 	3 = RBX
> > > > 	4 = RSP
> > > > 	5 = RBP
> > > > 	6 = RSI
> > > > 	7 = RDI
> > > > 	8–15 represent R8–R15, respectively...
> > > > 
> > > > Thus unless we add RBP to 'struct tdx_module_args', it's impossible to re-order
> > > > the structure to match KVM's layout.
> > > 
> > > Adding RBP to the struct shouldn't be a problem, we'll just not use it.
> > > Same as RSP, nobody sane would expect that to be used. If you worry
> > > about it you can give them funny names like:
> > > 
> > > struct tdx_module_args {
> > > 	unsigned long ax;
> > > 	unsigned long cx;
> > > 	unsigned long dx;
> > > 	unsigned long bx;
> > > 	unsigned long __sp_unused;
> > > 	unsigned long __bp_unused;
> > > 	unsigned long si;
> > > 	unsigned long di;
> > > 	...
> > > };
> > > 
> > > I mean, at this point the whole thing is just 128 bytes of data anyway.
> > 
> > Sure I can do.
> > 
> > How about adding an additional patch on top of this series?  
> > 
> > For instance, below patch (compile only):
> > 
> > From c63d01bf91fe23f1e2d2e085644326bdee114d49 Mon Sep 17 00:00:00 2001
> > From: Kai Huang <kai.huang@intel.com>
> > Date: Fri, 21 Jul 2023 22:06:31 +1200
> > Subject: [PATCH] x86/tdx: Add __seamcall_saved_ret() for TDH.VP.ENTER
> > 
> > For TDX guest, KVM uses TDH.VP.ENTER SEAMCALL leaf to enter the guest.
> > When TDH.VP.ENTER returns to KVM due to TDG.VP.VMCALL from the TDX
> > guest, all RCX/RDX/RBX/RDI/RSI/R8-R15 are valid output registers, and
> > the following TDH.VP.ENTER also uses all those registers as input.
> > 
> > Introduce __seamcall_saved_ret(), which uses all above registers as
> > both input/output, for KVM to support TDH.VP.ENTER.
> > 
> > Also, KVM caches guest's GPRs in 'kvm_vcpu_arch::regs[]', which follows
> > follows the "register index" hardware layout of x86 GPRs.  However the
> > __seamcall_saved_ret() takes the pointer of 'struct tdx_module_args' as
> > argument, thus there's a mismatch here.
> > 
> > One option is KVM to copy input registers from 'vcpu::regs[]' to a
> > 'struct tdx_module_args' on the stack and use that to make the SEAMCALL,
> > but such memory copy isn't desired and should be avoided if possible.
> > It's not feasible to change KVM's 'vcpu::regs[]' layout due to various
> > reasons (e.g., emulation code uses decoded register index as array index
> > to access the register).  Therefore, adjust 'struct tdx_module_args' to
> > match KVM's 'vcpu::regs[]' so that KVM can simply do below:
> > 
> >         seamcall_saved_ret(TDH.VP.ENTER,
> >                         (struct tdx_module_args *)vcpu->arch->regs);
> > 
> > Note RAX/RSP/RBP are not used by the TDX_MODULE_CALL assembly, but they
> > are necessary in order match the layout of 'struct tdx_module_args' to
> > KVM's 'vcpu::regs[]'.  Thus add them to the structure, but name them as
> > *_unused.  Also don't include them to asm-offset.c so that any misuse of
> > them in the assembly would result in build error.
> > 
> > Signed-off-by: Kai Huang <kai.huang@intel.com>
> > ---
> >  arch/x86/include/asm/shared/tdx.h | 19 +++++++++++++------
> >  arch/x86/virt/vmx/tdx/seamcall.S  | 19 +++++++++++++++++++
> >  2 files changed, 32 insertions(+), 6 deletions(-)
> > 
> > diff --git a/arch/x86/include/asm/shared/tdx.h
> > b/arch/x86/include/asm/shared/tdx.h
> > index 74fc466dfdcd..8d1427562c63 100644
> > --- a/arch/x86/include/asm/shared/tdx.h
> > +++ b/arch/x86/include/asm/shared/tdx.h
> > @@ -58,24 +58,31 @@
> >   * Used in __tdcall*() to gather the input/output registers' values of the
> >   * TDCALL instruction when requesting services from the TDX module. This is a
> >   * software only structure and not part of the TDX module/VMM ABI
> > + *
> > + * Note those *_unused are not used by the TDX_MODULE_CALL assembly.
> > + * The layout of this structure also matches KVM's kvm_vcpu_arch::regs[]
> > + * layout, which follows the "register index" order of x86 GPRs.  KVM
> > + * then can simply type cast kvm_vcpu_arch::regs[] to this structure to
> > + * avoid the extra memory copy between two structures when making
> > + * TDH.VP.ENTER SEAMCALL.
> >   */
> >  struct tdx_module_args {
> > -       /* callee-clobbered */
> > +       u64 rax_unused;
> >         u64 rcx;
> >         u64 rdx;
> > +       u64 rbx;
> > +       u64 rsp_unused;
> > +       u64 rbp_unused;
> > +       u64 rsi;
> > +       u64 rdi;
> >         u64 r8;
> >         u64 r9;
> > -       /* extra callee-clobbered */
> >         u64 r10;
> >         u64 r11;
> > -       /* callee-saved + rdi/rsi */
> >         u64 r12;
> >         u64 r13;
> >         u64 r14;
> >         u64 r15;
> > -       u64 rbx;
> > -       u64 rdi;
> > -       u64 rsi;
> >  }; 
> > 
> > /* Used to communicate with the TDX module */
> > diff --git a/arch/x86/virt/vmx/tdx/seamcall.S b/arch/x86/virt/vmx/tdx/seamcall.S
> > index b32934837f16..f251ebadb014 100644
> > --- a/arch/x86/virt/vmx/tdx/seamcall.S
> > +++ b/arch/x86/virt/vmx/tdx/seamcall.S
> > @@ -40,3 +40,22 @@ SYM_FUNC_END(__seamcall)
> >  SYM_FUNC_START(__seamcall_ret)
> >         TDX_MODULE_CALL host=1 ret=1
> >  SYM_FUNC_END(__seamcall_ret)
> > +
> > +/*
> > + * __seamcall_saved_ret() - Host-side interface functions to SEAM software
> > + * (the P-SEAMLDR or the TDX module), with saving output registers to the
> > + * 'struct tdx_module_args' used as input.
> > + *
> > + * __seamcall_saved_ret() function ABI:
> > + *
> > + * @fn   (RDI)  - SEAMCALL Leaf number, moved to RAX
> > + * @args (RSI)  - struct tdx_module_args for input and output
> > + *
> > + * All registers in @args are used as input/output registers.
> > + *
> > + * Return (via RAX) TDX_SEAMCALL_VMFAILINVALID if the SEAMCALL itself
> > + * fails, or the completion status of the SEAMCALL leaf function.
> > + */
> > +SYM_FUNC_START(__seamcall_ret)
> > +       TDX_MODULE_CALL host=1 ret=1 saved=1
> > +SYM_FUNC_END(__seamcall_ret)
> 
> Sorry should be __seamcall_saved_ret.
> 
> > -- 
> > 2.41.0
> > 
> > 
> 
> Sorry missing the declaration of __seamcall_saved_ret():
> 
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -80,6 +80,7 @@ static inline long tdx_kvm_hypercall(unsigned int nr, unsigned
> long p1,
>  #ifdef CONFIG_INTEL_TDX_HOST
>  u64 __seamcall(u64 fn, struct tdx_module_args *args);
>  u64 __seamcall_ret(u64 fn, struct tdx_module_args *args);
> +u64 __seamcall_saved_ret(u64 fn, struct tdx_module_args *args);
> 
> And perhaps we should adjust the order of registers in asm-offset.c to match the
> change to the 'struct tdx_module_args'?
> 
> --- a/arch/x86/kernel/asm-offsets.c
> +++ b/arch/x86/kernel/asm-offsets.c
> @@ -70,6 +70,9 @@ static void __used common(void)
>         BLANK();
>         OFFSET(TDX_MODULE_rcx, tdx_module_args, rcx);
>         OFFSET(TDX_MODULE_rdx, tdx_module_args, rdx);
> +       OFFSET(TDX_MODULE_rbx, tdx_module_args, rbx);
> +       OFFSET(TDX_MODULE_rsi, tdx_module_args, rsi);
> +       OFFSET(TDX_MODULE_rdi, tdx_module_args, rdi);
>         OFFSET(TDX_MODULE_r8,  tdx_module_args, r8);
>         OFFSET(TDX_MODULE_r9,  tdx_module_args, r9);
>         OFFSET(TDX_MODULE_r10, tdx_module_args, r10);
> @@ -78,9 +81,6 @@ static void __used common(void)
>         OFFSET(TDX_MODULE_r13, tdx_module_args, r13);
>         OFFSET(TDX_MODULE_r14, tdx_module_args, r14);
>         OFFSET(TDX_MODULE_r15, tdx_module_args, r15);
> -       OFFSET(TDX_MODULE_rbx, tdx_module_args, rbx);
> -       OFFSET(TDX_MODULE_rdi, tdx_module_args, rdi);
> -       OFFSET(TDX_MODULE_rsi, tdx_module_args, rsi);
> 

Damn.. I think it's better to split this into two patches:

1) Introduce __seamcall_saved_ret() for VP.ENTER
2) Adjust 'struct tdx_module_args' layout

Because 1) is mandatory to support VP.ENTER, but 2) theoretically is an
optimization.

Then perhaps 1) can even be merged to patch "x86/virt/tdx: Wire up basic
SEAMCALL functions".

I'll make those patches and test the VP.ENTER actually works using the adjusted
'struct tdx_module_args' layout, and post v3 when done.

Thanks again Peter, and let me know if you have any comments here.