Re: [PATCH v2 02/17] x86/virt/tdx: Configure add-on features on TDX module init and update
From: Xu Yilun
Date: Thu Jun 25 2026 - 02:34:22 EST
On Wed, Jun 24, 2026 at 03:10:37PM -0700, Peter Fang wrote:
> On Wed, Jun 24, 2026 at 08:00:39PM +0800, Xu Yilun wrote:
> > > There's also zero stopping us from putting version in args:
> > >
> > > struct tdx_module_args args = {};
> > > int ret;
> > >
> > > if (tdx_addon_feature0) {
> > > args.r9 = tdx_addon_feature0;
> > > args.version = 1;
> > > }
> > >
> > > ret = seamcall_prerr(TDH_SYS_UPDATE, &args);
> > >
> > > Eh?
> > >
> > > That gives args.version==0 in all the normal cases which just happens to
> > > be the exact behavior we want. It also avoids having to plumb version
> > > through all the seamcall*() wrappers.
> >
> > Ah, on 2nd reading, I'm pretty sure now I understand your logical argument in
> > patch 1 and 2. It's good to me. I append my diff at the end.
> >
>
> [ ... ]
>
> > diff --git a/arch/x86/virt/vmx/tdx/tdxcall.S b/arch/x86/virt/vmx/tdx/tdxcall.S
> > index 016a2a1ec1d6..d1d3d40c5614 100644
> > --- a/arch/x86/virt/vmx/tdx/tdxcall.S
> > +++ b/arch/x86/virt/vmx/tdx/tdxcall.S
> > @@ -48,6 +48,14 @@
> > /* Move Leaf ID to RAX */
> > mov %rdi, %rax
> >
> > + /*
> > + * Extract the version from 'struct tdx_module_args', append it to
> > + * RAX[23:16]
> > + */
> > + movzbl TDX_MODULE_version(%rsi), %ecx
> > + shll $16, %ecx
> > + orq %rcx, %rax
> > +
> > /* Move other input regs from 'struct tdx_module_args' */
> > movq TDX_MODULE_rcx(%rsi), %rcx
> > movq TDX_MODULE_rdx(%rsi), %rdx
>
> This approach looks much cleaner to me. Would it be better to have a
> small C helper to encode the final RAX value instead of operating on RAX
> directly in asm? Looking at the May 2026 edition of the ABI spec,
> SEAMCALL RAX encoding is starting to get quite complex. Just thinking
> about this from a readability standpoint.
I'm also good to it. I made some diff for your proposal, Some additional
effort here is to update some comments and parameter names, to reflect
the differences between "function/func/fn" (the unversioned number) and
the final composite "fn_code" for RAX.
-----8<-------
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index f20e91d7ac35..c26eca18fded 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -143,6 +143,8 @@ struct tdx_module_args {
u64 rbx;
u64 rdi;
u64 rsi;
+ /* for leaf encoding */
+ u8 version;
};
/* 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 6854c52c374b..5cf3993e98f4 100644
--- a/arch/x86/virt/vmx/tdx/seamcall.S
+++ b/arch/x86/virt/vmx/tdx/seamcall.S
@@ -10,8 +10,8 @@
*
* __seamcall() function ABI:
*
- * @fn (RDI) - SEAMCALL Leaf number, moved to RAX
- * @args (RSI) - struct tdx_module_args for input
+ * @fn_code (RDI) - SEAMCALL composite leaf code, moved to RAX
+ * @args (RSI) - struct tdx_module_args for input
*
* Only RCX/RDX/R8-R11 are used as input registers.
*
@@ -29,8 +29,8 @@ SYM_FUNC_END(__seamcall)
*
* __seamcall_ret() function ABI:
*
- * @fn (RDI) - SEAMCALL Leaf number, moved to RAX
- * @args (RSI) - struct tdx_module_args for input and output
+ * @fn_code (RDI) - SEAMCALL composite leaf code, moved to RAX
+ * @args (RSI) - struct tdx_module_args for input and output
*
* Only RCX/RDX/R8-R11 are used as input/output registers.
*
@@ -51,8 +51,8 @@ SYM_FUNC_END(__seamcall_ret)
*
* __seamcall_saved_ret() function ABI:
*
- * @fn (RDI) - SEAMCALL Leaf number, moved to RAX
- * @args (RSI) - struct tdx_module_args for input and output
+ * @fn_code (RDI) - SEAMCALL composite leaf code, moved to RAX
+ * @args (RSI) - struct tdx_module_args for input and output
*
* All registers in @args are used as input/output registers.
*
diff --git a/arch/x86/virt/vmx/tdx/seamcall_internal.h b/arch/x86/virt/vmx/tdx/seamcall_internal.h
index be5f446467df..bb17d965b453 100644
--- a/arch/x86/virt/vmx/tdx/seamcall_internal.h
+++ b/arch/x86/virt/vmx/tdx/seamcall_internal.h
@@ -11,17 +11,28 @@
#ifndef _X86_VIRT_SEAMCALL_INTERNAL_H
#define _X86_VIRT_SEAMCALL_INTERNAL_H
+#include <linux/bitfield.h>
#include <linux/printk.h>
#include <linux/types.h>
#include <asm/archrandom.h>
#include <asm/processor.h>
#include <asm/tdx.h>
-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);
+u64 __seamcall(u64 fn_code, struct tdx_module_args *args);
+u64 __seamcall_ret(u64 fn_code, struct tdx_module_args *args);
+u64 __seamcall_saved_ret(u64 fn_code, struct tdx_module_args *args);
-typedef u64 (*sc_func_t)(u64 fn, struct tdx_module_args *args);
+typedef u64 (*sc_func_t)(u64 fn_code, struct tdx_module_args *args);
+
+#define SEAMCALL_VERSION_MASK GENMASK_U64(23, 16)
+
+static __always_inline u64 __seamcall_fn_encoding(sc_func_t func, u64 fn,
+ struct tdx_module_args *args)
+{
+ FIELD_MODIFY(SEAMCALL_VERSION_MASK, &fn, args->version);
+
+ return func(fn, args);
+}
static __always_inline u64 __seamcall_dirty_cache(sc_func_t func, u64 fn,
struct tdx_module_args *args)
@@ -39,7 +50,7 @@ static __always_inline u64 __seamcall_dirty_cache(sc_func_t func, u64 fn,
*/
this_cpu_write(cache_state_incoherent, true);
- return func(fn, args);
+ return __seamcall_fn_encoding(func, fn, args);
}
static __always_inline u64 sc_retry(sc_func_t func, u64 fn,
diff --git a/arch/x86/virt/vmx/tdx/tdxcall.S b/arch/x86/virt/vmx/tdx/tdxcall.S
index 016a2a1ec1d6..b0f7867bcd1c 100644
--- a/arch/x86/virt/vmx/tdx/tdxcall.S
+++ b/arch/x86/virt/vmx/tdx/tdxcall.S
@@ -24,7 +24,7 @@
*-------------------------------------------------------------------------
* Input Registers:
*
- * RAX - TDCALL/SEAMCALL Leaf number.
+ * RAX - TDCALL/SEAMCALL composite Leaf code.
* RCX,RDX,RDI,RSI,RBX,R8-R15 - TDCALL/SEAMCALL Leaf specific input registers.
*
* Output Registers:
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 6a1c4fe202bb..8c1a5b7f603a 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -1019,7 +1019,6 @@ static __init void set_tdx_addon_features(void)
static __init int config_tdx_module(struct tdmr_info_list *tdmr_list,
u64 global_keyid)
{
- u64 seamcall_fn = TDH_SYS_CONFIG_V0;
struct tdx_module_args args = {};
u64 *tdmr_pa_array;
size_t array_sz;
@@ -1042,18 +1041,18 @@ static __init int config_tdx_module(struct tdmr_info_list *tdmr_list,
for (i = 0; i < tdmr_list->nr_consumed_tdmrs; i++)
tdmr_pa_array[i] = __pa(tdmr_entry(tdmr_list, i));
+ set_tdx_addon_features();
+
args.rcx = __pa(tdmr_pa_array);
args.rdx = tdmr_list->nr_consumed_tdmrs;
args.r8 = global_keyid;
- set_tdx_addon_features();
-
if (tdx_addon_feature0) {
args.r9 = tdx_addon_feature0;
- seamcall_fn = TDH_SYS_CONFIG;
+ args.version = 1;
}
- ret = seamcall_prerr(seamcall_fn, &args);
+ ret = seamcall_prerr(TDH_SYS_CONFIG, &args);
/* Free the array as it is not required anymore. */
kfree(tdmr_pa_array);
@@ -1515,16 +1514,15 @@ int tdx_module_shutdown(void)
int tdx_module_run_update(void)
{
- u64 seamcall_fn = TDH_SYS_UPDATE_V0;
struct tdx_module_args args = {};
int ret;
if (tdx_addon_feature0) {
args.r9 = tdx_addon_feature0;
- seamcall_fn = TDH_SYS_UPDATE;
+ args.version = 1;
}
- ret = seamcall_prerr(seamcall_fn, &args);
+ ret = seamcall_prerr(TDH_SYS_UPDATE, &args);
if (ret)
return ret;
@@ -2112,6 +2110,7 @@ u64 tdh_vp_init(struct tdx_vp *vp, u64 initial_rcx, u32 x2apicid)
.rcx = vp->tdvpr_pa,
.rdx = initial_rcx,
.r8 = x2apicid,
+ .version = 1,
};
return seamcall(TDH_VP_INIT, &args);
diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
index 2deb0a5c902e..1f43d2eb2345 100644
--- a/arch/x86/virt/vmx/tdx/tdx.h
+++ b/arch/x86/virt/vmx/tdx/tdx.h
@@ -2,7 +2,6 @@
#ifndef _X86_VIRT_TDX_H
#define _X86_VIRT_TDX_H
-#include <linux/bitfield.h>
#include <linux/bits.h>
/*
@@ -12,18 +11,6 @@
* architectural definitions come first.
*/
-/*
- * SEAMCALL leaf:
- *
- * Bit 15:0 Leaf number
- * Bit 23:16 Version number
- */
-#define SEAMCALL_LEAF GENMASK(15, 0)
-#define SEAMCALL_VER GENMASK(23, 16)
-
-#define SEAMCALL_LEAF_VER(l, v) (FIELD_PREP(SEAMCALL_LEAF, l) | \
- FIELD_PREP(SEAMCALL_VER, v))
-
/*
* TDX module SEAMCALL leaf functions
*/
@@ -44,7 +31,7 @@
#define TDH_VP_CREATE 10
#define TDH_MNG_KEY_FREEID 20
#define TDH_MNG_INIT 21
-#define TDH_VP_INIT SEAMCALL_LEAF_VER(22, 1)
+#define TDH_VP_INIT 22
#define TDH_PHYMEM_PAGE_RDMD 24
#define TDH_VP_RD 26
#define TDH_PHYMEM_PAGE_RECLAIM 28
@@ -58,11 +45,9 @@
#define TDH_PHYMEM_CACHE_WB 40
#define TDH_PHYMEM_PAGE_WBINVD 41
#define TDH_VP_WR 43
-#define TDH_SYS_CONFIG_V0 45
-#define TDH_SYS_CONFIG SEAMCALL_LEAF_VER(TDH_SYS_CONFIG_V0, 1)
+#define TDH_SYS_CONFIG 45
#define TDH_SYS_SHUTDOWN 52
-#define TDH_SYS_UPDATE_V0 53
-#define TDH_SYS_UPDATE SEAMCALL_LEAF_VER(TDH_SYS_UPDATE_V0, 1)
+#define TDH_SYS_UPDATE 53
#define TDH_EXT_INIT 60
#define TDH_EXT_MEM_ADD 61
#define TDH_SYS_DISABLE 69