linux-kernel - [patch 3/7] x86/fpu/xsave: Initialize offset/size cache early

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Date:   Thu, 24 Mar 2022 14:47:11 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, "Chang S. Bae" <chang.seok.bae@...el.com>
Subject: [patch 3/7] x86/fpu/xsave: Initialize offset/size cache early

Reading XSTATE feature information from CPUID over and over does not make
sense. The information has to be cached anyway, so it can be done early.

This prepares for runtime calculation of XSTATE offsets and allows
consolidation of the size calculation functions in a later step.

Rename the function while at it as it does not setup any features.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/kernel/fpu/xstate.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -180,7 +180,7 @@ static bool xfeature_enabled(enum xfeatu
  * Record the offsets and sizes of various xstates contained
  * in the XSAVE state memory layout.
  */
-static void __init setup_xstate_features(void)
+static void __init setup_xstate_cache(void)
 {
 	u32 eax, ebx, ecx, edx, i;
 	/* start at the beginning of the "extended state" */
@@ -390,7 +390,6 @@ static void __init setup_init_fpu_buf(vo
 	if (!boot_cpu_has(X86_FEATURE_XSAVE))
 		return;

-	setup_xstate_features();
 	print_xstate_features();

 	xstate_init_xcomp_bv(&init_fpstate.regs.xsave, fpu_kernel_cfg.max_features);
@@ -906,6 +905,10 @@ void __init fpu__init_system_xstate(unsi

 	/* Enable xstate instructions to be able to continue with initialization: */
 	fpu__init_cpu_xstate();
+
+	/* Cache size, offset and flags for initialization */
+	setup_xstate_cache();
+
 	err = init_xstate_size();
 	if (err)
 		goto out_disable;