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From: Yu-cheng Yu <yu-cheng.yu@intel.com>
To: linux-kernel@vger.kernel.org, x86@kernel.org,
	"H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Tony Luck <tony.luck@intel.com>,
	Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@alien8.de>,
	Rik van Riel <riel@surriel.com>,
	"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Fenghua Yu <fenghua.yu@intel.com>,
	Peter Zijlstra <peterz@infradead.org>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Subject: [PATCH 4/6] x86/fpu/xstate: Introduce XSAVES supervisor states
Date: Wed, 25 Sep 2019 08:10:20 -0700
Message-ID: <20190925151022.21688-5-yu-cheng.yu@intel.com> (raw)
In-Reply-To: <20190925151022.21688-1-yu-cheng.yu@intel.com>

Enable XSAVES supervisor states by setting MSR_IA32_XSS bits according to
CPUID enumeration results.  Also revise comments at various places.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
---
 arch/x86/kernel/fpu/xstate.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index b7f2808dd3f4..a183c319d808 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -233,13 +233,14 @@ void fpu__init_cpu_xstate(void)
 	 * states can be set here.
 	 */
 	xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask_user());
+
+	/*
+	 * MSR_IA32_XSS sets supervisor states managed by XSAVES.
+	 */
+	if (boot_cpu_has(X86_FEATURE_XSAVES))
+		wrmsrl(MSR_IA32_XSS, xfeatures_mask_supervisor());
 }
 
-/*
- * Note that in the future we will likely need a pair of
- * functions here: one for user xstates and the other for
- * system xstates.  For now, they are the same.
- */
 static int xfeature_enabled(enum xfeature xfeature)
 {
 	return !!(xfeatures_mask_all & (1UL << xfeature));
@@ -623,9 +624,6 @@ static void do_extra_xstate_size_checks(void)
  * the size of the *user* states.  If we use it to size a buffer
  * that we use 'XSAVES' on, we could potentially overflow the
  * buffer because 'XSAVES' saves system states too.
- *
- * Note that we do not currently set any bits on IA32_XSS so
- * 'XCR0 | IA32_XSS == XCR0' for now.
  */
 static unsigned int __init get_xsaves_size(void)
 {
@@ -748,7 +746,11 @@ void __init fpu__init_system_xstate(void)
 	cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
 	xfeatures_mask_all = eax + ((u64)edx << 32);
 
-	/* Place supervisor features in xfeatures_mask_all here */
+	/*
+	 * Find supervisor xstates supported by the processor.
+	 */
+	cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
+	xfeatures_mask_all |= ecx + ((u64)edx << 32);
 
 	if ((xfeatures_mask_user() & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
 		/*
@@ -788,9 +790,10 @@ void __init fpu__init_system_xstate(void)
 	setup_xstate_comp();
 	print_xstate_offset_size();
 
-	pr_info("x86/fpu: Enabled xstate features 0x%llx: user 0x%llx, context size is %d bytes, using '%s' format.\n",
+	pr_info("x86/fpu: Enabled xstate features 0x%llx: user 0x%llx and supervisor %llx, context size is %d bytes, using '%s' format.\n",
 		xfeatures_mask_all,
 		xfeatures_mask_user(),
+		xfeatures_mask_supervisor(),
 		fpu_kernel_xstate_size,
 		boot_cpu_has(X86_FEATURE_XSAVES) ? "compacted" : "standard");
 	return;
@@ -810,6 +813,13 @@ void fpu__resume_cpu(void)
 	 */
 	if (boot_cpu_has(X86_FEATURE_XSAVE))
 		xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask_user());
+
+	/*
+	 * Restore IA32_XSS. The same CPUID bit enumerates support
+	 * of XSAVES and MSR_IA32_XSS.
+	 */
+	if (boot_cpu_has(X86_FEATURE_XSAVES))
+		wrmsrl(MSR_IA32_XSS, xfeatures_mask_supervisor());
 }
 
 /*
-- 
2.17.1


  parent reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-25 15:10 [PATCH 0/6] Support " Yu-cheng Yu
2019-09-25 15:10 ` [PATCH 1/6] x86/fpu/xstate: Fix small issues before adding supervisor xstates Yu-cheng Yu
2019-10-09 15:58   ` Borislav Petkov
2019-11-22 21:22     ` Yu-cheng Yu
2019-11-22 21:54       ` Borislav Petkov
2019-09-25 15:10 ` [PATCH 2/6] x86/fpu/xstate: Define new macros for supervisor and user xstates Yu-cheng Yu
2019-10-09 16:17   ` Borislav Petkov
2019-09-25 15:10 ` [PATCH 3/6] x86/fpu/xstate: Separate user and supervisor xfeatures mask Yu-cheng Yu
2019-10-09 16:59   ` Borislav Petkov
2019-09-25 15:10 ` Yu-cheng Yu [this message]
2019-10-09 17:10   ` [PATCH 4/6] x86/fpu/xstate: Introduce XSAVES supervisor states Borislav Petkov
2019-09-25 15:10 ` [PATCH 5/6] x86/fpu/xstate: Define new functions for clearing fpregs and xstates Yu-cheng Yu
2019-10-09 17:28   ` Borislav Petkov
2019-09-25 15:10 ` [PATCH 6/6] x86/fpu/xstate: Rename validate_xstate_header() to validate_xstate_header_from_user() Yu-cheng Yu
2019-10-09 17:31   ` Borislav Petkov
2019-10-09 22:10     ` Yu-cheng Yu

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