linux-kernel - [PATCH RFC v2 6/9] x86/fpu/apx: Define APX state component

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Message-ID: <20250320234301.8342-7-chang.seok.bae@intel.com>
Date: Thu, 20 Mar 2025 16:42:57 -0700
From: "Chang S. Bae" <chang.seok.bae@...el.com>
To: linux-kernel@...r.kernel.org
Cc: x86@...nel.org,
	tglx@...utronix.de,
	mingo@...hat.com,
	bp@...en8.de,
	dave.hansen@...ux.intel.com,
	chang.seok.bae@...el.com
Subject: [PATCH RFC v2 6/9] x86/fpu/apx: Define APX state component

The Advanced Performance Extensions (APX) feature flag was previously
defined. This feature is associated with a new state component number 19.
To support APX, it is essential to define this xstate component and
implement the necessary sanity checks.

Define the new component number, state name, and those register data
type. Then, extend the size checker to validate the register data type
and explicitly set the APX feature flag as a dependency for the new
component in xsave_cpuid_features[].

Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
---
RFC-V1 -> RFC-V2:
* Remove the ordering table change, as it is now dynamically populated.
---
 arch/x86/include/asm/fpu/types.h | 9 +++++++++
 arch/x86/kernel/fpu/xstate.c     | 3 +++
 2 files changed, 12 insertions(+)

diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index de16862bf230..97310df3ea13 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -125,6 +125,7 @@ enum xfeature {
 	XFEATURE_RSRVD_COMP_16,
 	XFEATURE_XTILE_CFG,
 	XFEATURE_XTILE_DATA,
+	XFEATURE_APX,
 
 	XFEATURE_MAX,
 };
@@ -145,6 +146,7 @@ enum xfeature {
 #define XFEATURE_MASK_LBR		(1 << XFEATURE_LBR)
 #define XFEATURE_MASK_XTILE_CFG		(1 << XFEATURE_XTILE_CFG)
 #define XFEATURE_MASK_XTILE_DATA	(1 << XFEATURE_XTILE_DATA)
+#define XFEATURE_MASK_APX		(1 << XFEATURE_APX)
 
 #define XFEATURE_MASK_FPSSE		(XFEATURE_MASK_FP | XFEATURE_MASK_SSE)
 #define XFEATURE_MASK_AVX512		(XFEATURE_MASK_OPMASK \
@@ -303,6 +305,13 @@ struct xtile_data {
 	struct reg_1024_byte		tmm;
 } __packed;
 
+/*
+ * State component 19: 8B extended general purpose register.
+ */
+struct apx_state {
+	u64				egpr[16];
+} __packed;
+
 /*
  * State component 10 is supervisor state used for context-switching the
  * PASID state.
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 46c45e2f2a5a..2a270683a762 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -63,6 +63,7 @@ static const char *xfeature_names[] =
 	"unknown xstate feature",
 	"AMX Tile config",
 	"AMX Tile data",
+	"APX registers",
 	"unknown xstate feature",
 };
 
@@ -81,6 +82,7 @@ static unsigned short xsave_cpuid_features[] __initdata = {
 	[XFEATURE_CET_USER]			= X86_FEATURE_SHSTK,
 	[XFEATURE_XTILE_CFG]			= X86_FEATURE_AMX_TILE,
 	[XFEATURE_XTILE_DATA]			= X86_FEATURE_AMX_TILE,
+	[XFEATURE_APX]				= X86_FEATURE_APX,
 };
 
 static unsigned int xstate_offsets[XFEATURE_MAX] __ro_after_init =
@@ -570,6 +572,7 @@ static bool __init check_xstate_against_struct(int nr)
 	case XFEATURE_XTILE_CFG:  return XCHECK_SZ(sz, nr, struct xtile_cfg);
 	case XFEATURE_CET_USER:	  return XCHECK_SZ(sz, nr, struct cet_user_state);
 	case XFEATURE_XTILE_DATA: check_xtile_data_against_struct(sz); return true;
+	case XFEATURE_APX:        return XCHECK_SZ(sz, nr, struct apx_state);
 	default:
 		XSTATE_WARN_ON(1, "No structure for xstate: %d\n", nr);
 		return false;
-- 
2.45.2