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Groups > linux.kernel > #1273050 > unrolled thread

[RFC PATCH 0/2] x86/fpu: Remove xstate_fault()

Started byBorislav Petkov <bp@alien8.de>
First post2015-11-19 12:30 +0100
Last post2015-11-24 10:40 +0100
Articles 3 — 2 participants

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  [RFC PATCH 0/2] x86/fpu: Remove xstate_fault() Borislav Petkov <bp@alien8.de> - 2015-11-19 12:30 +0100
    [RFC PATCH 2/2] x86/fpu: Get rid of xstate_fault() Borislav Petkov <bp@alien8.de> - 2015-11-19 12:30 +0100
      [tip:x86/fpu] x86/fpu: Get rid of xstate_fault() tip-bot for Borislav Petkov <tipbot@zytor.com> - 2015-11-24 10:40 +0100

#1273050 — [RFC PATCH 0/2] x86/fpu: Remove xstate_fault()

FromBorislav Petkov <bp@alien8.de>
Date2015-11-19 12:30 +0100
Subject[RFC PATCH 0/2] x86/fpu: Remove xstate_fault()
Message-ID<qwvzA-by-15@gated-at.bofh.it>
From: Borislav Petkov <bp@suse.de>

Hi,

so that xstate_fault() thing did cause trouble in the past, see

  06c8173eb92b ("x86/fpu/xsaves: Fix improper uses of __ex_table")

So lemme kill it.

I had an earlier version of that patch, here's an updated one and split
into two for better digestion.

The guest boots fine so far, I need to run it on the rest of the hw to
check everything's fine.

Borislav Petkov (2):
  x86/fpu: Add an XSTATE_OP macro
  x86/fpu: Get rid of xstate_fault()

 arch/x86/include/asm/fpu/internal.h | 173 +++++++++++++++++-------------------
 1 file changed, 83 insertions(+), 90 deletions(-)

-- 
2.3.5

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#1273052 — [RFC PATCH 2/2] x86/fpu: Get rid of xstate_fault()

FromBorislav Petkov <bp@alien8.de>
Date2015-11-19 12:30 +0100
Subject[RFC PATCH 2/2] x86/fpu: Get rid of xstate_fault()
Message-ID<qwvzB-by-29@gated-at.bofh.it>
In reply to#1273050
From: Borislav Petkov <bp@suse.de>

Add macros for the alternative XSAVE*/XRSTOR* operations which contain
the fault handling and use them. Kill xstate_fault().

Also, copy_xregs_to_kernel() didn't have the extended state as memory
reference in the asm.

Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/include/asm/fpu/internal.h | 105 ++++++++++++++++++------------------
 1 file changed, 52 insertions(+), 53 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 709a3df8ab37..eadcdd5bb946 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -224,19 +224,6 @@ static inline void copy_fxregs_to_kernel(struct fpu *fpu)
 #define XRSTOR		".byte " REX_PREFIX "0x0f,0xae,0x2f"
 #define XRSTORS		".byte " REX_PREFIX "0x0f,0xc7,0x1f"
 
-/* xstate instruction fault handler: */
-#define xstate_fault(__err)		\
-					\
-	".section .fixup,\"ax\"\n"	\
-					\
-	"3:  movl $-2,%[_err]\n"	\
-	"    jmp  2b\n"			\
-					\
-	".previous\n"			\
-					\
-	_ASM_EXTABLE(1b, 3b)		\
-	: [_err] "=r" (__err)
-
 #define XSTATE_OP(op, st, lmask, hmask, err)				\
 	asm volatile("1:" op "\n\t"					\
 		     "xor %[err], %[err]\n"				\
@@ -250,6 +237,54 @@ static inline void copy_fxregs_to_kernel(struct fpu *fpu)
 		     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)	\
 		     : "memory")
 
+/*
+ * If XSAVES is enabled, it replaces XSAVEOPT because it supports a compact
+ * format and supervisor states in addition to modified optimization in
+ * XSAVEOPT.
+ *
+ * Otherwise, if XSAVEOPT is enabled, XSAVEOPT replaces XSAVE because XSAVEOPT
+ * supports modified optimization which is not supported by XSAVE.
+ *
+ * We use XSAVE as a fallback.
+ *
+ * The 661 label is defined in the ALTERNATIVE* macros as the address of the
+ * original instruction which gets replaced. We need to use it here as the
+ * address of the instruction where we might get an exception at.
+ */
+#define XSTATE_XSAVE(st, lmask, hmask, err)				\
+	asm volatile(ALTERNATIVE_2(XSAVE,				\
+				   XSAVEOPT, X86_FEATURE_XSAVEOPT,	\
+				   XSAVES,   X86_FEATURE_XSAVES)	\
+		     "\n"						\
+		     "xor %[err], %[err]\n"				\
+		     "3:\n"						\
+		     ".pushsection .fixup,\"ax\"\n"			\
+		     "4: movl $-2, %[err]\n"				\
+		     "jmp 3b\n"						\
+		     ".popsection\n"					\
+		     _ASM_EXTABLE(661b, 4b)				\
+		     : [err] "=r" (err)					\
+		     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)	\
+		     : "memory")
+
+/*
+ * Use XRSTORS to restore context if it is enabled. XRSTORS supports compact
+ * XSAVE area format.
+ */
+#define XSTATE_XRESTORE(st, lmask, hmask, err)				\
+	asm volatile(ALTERNATIVE(XRSTOR,				\
+				 XRSTORS, X86_FEATURE_XSAVES)		\
+		     "\n"						\
+		     "xor %[err], %[err]\n"				\
+		     "3:\n"						\
+		     ".pushsection .fixup,\"ax\"\n"			\
+		     "4: movl $-2, %[err]\n"				\
+		     "jmp 3b\n"						\
+		     ".popsection\n"					\
+		     _ASM_EXTABLE(661b, 4b)				\
+		     : [err] "=r" (err)					\
+		     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)	\
+		     : "memory")
 
 /*
  * This function is called only during boot time when x86 caps are not set
@@ -303,33 +338,11 @@ static inline void copy_xregs_to_kernel(struct xregs_state *xstate)
 	u64 mask = -1;
 	u32 lmask = mask;
 	u32 hmask = mask >> 32;
-	int err = 0;
+	int err;
 
 	WARN_ON(!alternatives_patched);
 
-	/*
-	 * If xsaves is enabled, xsaves replaces xsaveopt because
-	 * it supports compact format and supervisor states in addition to
-	 * modified optimization in xsaveopt.
-	 *
-	 * Otherwise, if xsaveopt is enabled, xsaveopt replaces xsave
-	 * because xsaveopt supports modified optimization which is not
-	 * supported by xsave.
-	 *
-	 * If none of xsaves and xsaveopt is enabled, use xsave.
-	 */
-	alternative_input_2(
-		"1:"XSAVE,
-		XSAVEOPT,
-		X86_FEATURE_XSAVEOPT,
-		XSAVES,
-		X86_FEATURE_XSAVES,
-		[xstate] "D" (xstate), "a" (lmask), "d" (hmask) :
-		"memory");
-	asm volatile("2:\n\t"
-		     xstate_fault(err)
-		     : "0" (err)
-		     : "memory");
+	XSTATE_XSAVE(xstate, lmask, hmask, err);
 
 	/* We should never fault when copying to a kernel buffer: */
 	WARN_ON_FPU(err);
@@ -342,23 +355,9 @@ static inline void copy_kernel_to_xregs(struct xregs_state *xstate, u64 mask)
 {
 	u32 lmask = mask;
 	u32 hmask = mask >> 32;
-	int err = 0;
+	int err;
 
-	/*
-	 * Use xrstors to restore context if it is enabled. xrstors supports
-	 * compacted format of xsave area which is not supported by xrstor.
-	 */
-	alternative_input(
-		"1: " XRSTOR,
-		XRSTORS,
-		X86_FEATURE_XSAVES,
-		"D" (xstate), "m" (*xstate), "a" (lmask), "d" (hmask)
-		: "memory");
-
-	asm volatile("2:\n"
-		     xstate_fault(err)
-		     : "0" (err)
-		     : "memory");
+	XSTATE_XRESTORE(xstate, lmask, hmask, err);
 
 	/* We should never fault when copying from a kernel buffer: */
 	WARN_ON_FPU(err);
-- 
2.3.5

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#1276218 — [tip:x86/fpu] x86/fpu: Get rid of xstate_fault()

Fromtip-bot for Borislav Petkov <tipbot@zytor.com>
Date2015-11-24 10:40 +0100
Subject[tip:x86/fpu] x86/fpu: Get rid of xstate_fault()
Message-ID<qyieU-6jd-79@gated-at.bofh.it>
In reply to#1273052
Commit-ID:  b7106fa0f29f9fd83d2d1905ab690d334ef855c1
Gitweb:     http://git.kernel.org/tip/b7106fa0f29f9fd83d2d1905ab690d334ef855c1
Author:     Borislav Petkov <bp@suse.de>
AuthorDate: Thu, 19 Nov 2015 12:25:26 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 24 Nov 2015 09:52:52 +0100

x86/fpu: Get rid of xstate_fault()

Add macros for the alternative XSAVE*/XRSTOR* operations which
contain the fault handling and use them. Kill xstate_fault().

Also, copy_xregs_to_kernel() didn't have the extended state as
memory reference in the asm.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1447932326-4371-3-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/include/asm/fpu/internal.h | 105 ++++++++++++++++++------------------
 1 file changed, 52 insertions(+), 53 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 709a3df..eadcdd5 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -224,19 +224,6 @@ static inline void copy_fxregs_to_kernel(struct fpu *fpu)
 #define XRSTOR		".byte " REX_PREFIX "0x0f,0xae,0x2f"
 #define XRSTORS		".byte " REX_PREFIX "0x0f,0xc7,0x1f"
 
-/* xstate instruction fault handler: */
-#define xstate_fault(__err)		\
-					\
-	".section .fixup,\"ax\"\n"	\
-					\
-	"3:  movl $-2,%[_err]\n"	\
-	"    jmp  2b\n"			\
-					\
-	".previous\n"			\
-					\
-	_ASM_EXTABLE(1b, 3b)		\
-	: [_err] "=r" (__err)
-
 #define XSTATE_OP(op, st, lmask, hmask, err)				\
 	asm volatile("1:" op "\n\t"					\
 		     "xor %[err], %[err]\n"				\
@@ -250,6 +237,54 @@ static inline void copy_fxregs_to_kernel(struct fpu *fpu)
 		     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)	\
 		     : "memory")
 
+/*
+ * If XSAVES is enabled, it replaces XSAVEOPT because it supports a compact
+ * format and supervisor states in addition to modified optimization in
+ * XSAVEOPT.
+ *
+ * Otherwise, if XSAVEOPT is enabled, XSAVEOPT replaces XSAVE because XSAVEOPT
+ * supports modified optimization which is not supported by XSAVE.
+ *
+ * We use XSAVE as a fallback.
+ *
+ * The 661 label is defined in the ALTERNATIVE* macros as the address of the
+ * original instruction which gets replaced. We need to use it here as the
+ * address of the instruction where we might get an exception at.
+ */
+#define XSTATE_XSAVE(st, lmask, hmask, err)				\
+	asm volatile(ALTERNATIVE_2(XSAVE,				\
+				   XSAVEOPT, X86_FEATURE_XSAVEOPT,	\
+				   XSAVES,   X86_FEATURE_XSAVES)	\
+		     "\n"						\
+		     "xor %[err], %[err]\n"				\
+		     "3:\n"						\
+		     ".pushsection .fixup,\"ax\"\n"			\
+		     "4: movl $-2, %[err]\n"				\
+		     "jmp 3b\n"						\
+		     ".popsection\n"					\
+		     _ASM_EXTABLE(661b, 4b)				\
+		     : [err] "=r" (err)					\
+		     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)	\
+		     : "memory")
+
+/*
+ * Use XRSTORS to restore context if it is enabled. XRSTORS supports compact
+ * XSAVE area format.
+ */
+#define XSTATE_XRESTORE(st, lmask, hmask, err)				\
+	asm volatile(ALTERNATIVE(XRSTOR,				\
+				 XRSTORS, X86_FEATURE_XSAVES)		\
+		     "\n"						\
+		     "xor %[err], %[err]\n"				\
+		     "3:\n"						\
+		     ".pushsection .fixup,\"ax\"\n"			\
+		     "4: movl $-2, %[err]\n"				\
+		     "jmp 3b\n"						\
+		     ".popsection\n"					\
+		     _ASM_EXTABLE(661b, 4b)				\
+		     : [err] "=r" (err)					\
+		     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)	\
+		     : "memory")
 
 /*
  * This function is called only during boot time when x86 caps are not set
@@ -303,33 +338,11 @@ static inline void copy_xregs_to_kernel(struct xregs_state *xstate)
 	u64 mask = -1;
 	u32 lmask = mask;
 	u32 hmask = mask >> 32;
-	int err = 0;
+	int err;
 
 	WARN_ON(!alternatives_patched);
 
-	/*
-	 * If xsaves is enabled, xsaves replaces xsaveopt because
-	 * it supports compact format and supervisor states in addition to
-	 * modified optimization in xsaveopt.
-	 *
-	 * Otherwise, if xsaveopt is enabled, xsaveopt replaces xsave
-	 * because xsaveopt supports modified optimization which is not
-	 * supported by xsave.
-	 *
-	 * If none of xsaves and xsaveopt is enabled, use xsave.
-	 */
-	alternative_input_2(
-		"1:"XSAVE,
-		XSAVEOPT,
-		X86_FEATURE_XSAVEOPT,
-		XSAVES,
-		X86_FEATURE_XSAVES,
-		[xstate] "D" (xstate), "a" (lmask), "d" (hmask) :
-		"memory");
-	asm volatile("2:\n\t"
-		     xstate_fault(err)
-		     : "0" (err)
-		     : "memory");
+	XSTATE_XSAVE(xstate, lmask, hmask, err);
 
 	/* We should never fault when copying to a kernel buffer: */
 	WARN_ON_FPU(err);
@@ -342,23 +355,9 @@ static inline void copy_kernel_to_xregs(struct xregs_state *xstate, u64 mask)
 {
 	u32 lmask = mask;
 	u32 hmask = mask >> 32;
-	int err = 0;
+	int err;
 
-	/*
-	 * Use xrstors to restore context if it is enabled. xrstors supports
-	 * compacted format of xsave area which is not supported by xrstor.
-	 */
-	alternative_input(
-		"1: " XRSTOR,
-		XRSTORS,
-		X86_FEATURE_XSAVES,
-		"D" (xstate), "m" (*xstate), "a" (lmask), "d" (hmask)
-		: "memory");
-
-	asm volatile("2:\n"
-		     xstate_fault(err)
-		     : "0" (err)
-		     : "memory");
+	XSTATE_XRESTORE(xstate, lmask, hmask, err);
 
 	/* We should never fault when copying from a kernel buffer: */
 	WARN_ON_FPU(err);
--
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