linux-kernel - [RFC PATCH 02/10] x86/fpu: Split fpu_xfd_enabled from fpu_state_size

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Message-Id: <20211203003636.11417-3-jiaxun.yang@flygoat.com>
Date:   Fri,  3 Dec 2021 00:36:28 +0000
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     x86@...nel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com,
        chang.seok.bae@...el.com, linux-kernel@...r.kernel.org,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Jiaxun Yang <j.yang-87@....ed.ac.uk>
Subject: [RFC PATCH 02/10] x86/fpu: Split fpu_xfd_enabled from fpu_state_size_dynamic

Following patches will make fpu_state_size_dynamic nolonger depend
on XFD, so split XFD related static branch from fpu_state_size_dynamic.

Also make fpu_state_size_dynamic available on both x86 and x86_64.

Signed-off-by: Jiaxun Yang <j.yang-87@....ed.ac.uk>
---
 arch/x86/include/asm/fpu/xstate.h | 11 +++++++++--
 arch/x86/kernel/fpu/core.c        |  3 ++-
 arch/x86/kernel/fpu/xstate.c      | 31 +++++++++++++++++++------------
 arch/x86/kernel/fpu/xstate.h      |  2 +-
 4 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index fb83534e92f6..c46d3dd591bd 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -111,15 +111,22 @@ void xrstors(struct xregs_state *xsave, u64 mask);
 
 int xfd_enable_feature(u64 xfd_err);
 
-#ifdef CONFIG_X86_64
 DECLARE_STATIC_KEY_FALSE(__fpu_state_size_dynamic);
 
 static __always_inline __pure bool fpu_state_size_dynamic(void)
 {
 	return static_branch_unlikely(&__fpu_state_size_dynamic);
 }
+
+#ifdef CONFIG_X86_64
+DECLARE_STATIC_KEY_FALSE(__fpu_xfd_enabled);
+
+static __always_inline __pure bool fpu_xfd_enabled(void)
+{
+	return static_branch_unlikely(&__fpu_xfd_enabled);
+}
 #else
-static __always_inline __pure bool fpu_state_size_dynamic(void)
+static __always_inline __pure bool fpu_xfd_enabled(void)
 {
 	return false;
 }
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index dd3777ac0443..88dbbbde7a3a 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -26,8 +26,9 @@
 #define CREATE_TRACE_POINTS
 #include <asm/trace/fpu.h>
 
-#ifdef CONFIG_X86_64
 DEFINE_STATIC_KEY_FALSE(__fpu_state_size_dynamic);
+#ifdef CONFIG_X86_64
+DEFINE_STATIC_KEY_FALSE(__fpu_xfd_enabled);
 DEFINE_PER_CPU(u64, xfd_state);
 #endif
 
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index d28829403ed0..353c661f8027 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -995,7 +995,7 @@ void fpu__resume_cpu(void)
 				     xfeatures_mask_independent());
 	}
 
-	if (fpu_state_size_dynamic())
+	if (fpu_xfd_enabled())
 		wrmsrl(MSR_IA32_XFD, current->thread.fpu.fpstate->xfd);
 }
 
@@ -1422,6 +1422,23 @@ void fpstate_clear_xstate_component(struct fpstate *fps, unsigned int xfeature)
 EXPORT_SYMBOL_GPL(fpstate_clear_xstate_component);
 #endif
 
+static int __init xstate_update_static_branch(void)
+{
+	if (fpu_kernel_cfg.max_features != fpu_kernel_cfg.default_features)
+		static_branch_enable(&__fpu_state_size_dynamic);
+
+#ifdef CONFIG_X86_64
+	/*
+	 * If init_fpstate.xfd has bits set then dynamic features are
+	 * available and the dynamic sizing must be enabled.
+	 */
+	if (init_fpstate.xfd)
+		static_branch_enable(&__fpu_xfd_enabled);
+#endif
+	return 0;
+}
+arch_initcall(xstate_update_static_branch)
+
 #ifdef CONFIG_X86_64
 
 #ifdef CONFIG_X86_DEBUG_FPU
@@ -1481,17 +1498,7 @@ void xfd_validate_state(struct fpstate *fpstate, u64 mask, bool rstor)
 }
 #endif /* CONFIG_X86_DEBUG_FPU */
 
-static int __init xfd_update_static_branch(void)
-{
-	/*
-	 * If init_fpstate.xfd has bits set then dynamic features are
-	 * available and the dynamic sizing must be enabled.
-	 */
-	if (init_fpstate.xfd)
-		static_branch_enable(&__fpu_state_size_dynamic);
-	return 0;
-}
-arch_initcall(xfd_update_static_branch)
+
 
 void fpstate_free(struct fpu *fpu)
 {
diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h
index 86ea7c0fa2f6..f6bebaeea4ad 100644
--- a/arch/x86/kernel/fpu/xstate.h
+++ b/arch/x86/kernel/fpu/xstate.h
@@ -140,7 +140,7 @@ static inline void xfd_validate_state(struct fpstate *fpstate, u64 mask, bool rs
 #ifdef CONFIG_X86_64
 static inline void xfd_update_state(struct fpstate *fpstate)
 {
-	if (fpu_state_size_dynamic()) {
+	if (fpu_xfd_enabled()) {
 		u64 xfd = fpstate->xfd;
 
 		if (__this_cpu_read(xfd_state) != xfd) {
-- 
2.30.2