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From: David Woodhouse <dwmw@amazon.co.uk>
To: arjan@linux.intel.com, tglx@linutronix.de, karahmed@amazon.de,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	tim.c.chen@linux.intel.com, bp@alien8.de, peterz@infradead.org,
	pbonzini@redhat.com, ak@linux.intel.com,
	torvalds@linux-foundation.org, gregkh@linux-foundation.org,
	dave.hansen@intel.com
Subject: [PATCH 3/3] x86/speculation: Simplify indirect_branch_prediction_barrier()
Date: Sat, 27 Jan 2018 16:24:34 +0000	[thread overview]
Message-ID: <1517070274-12128-4-git-send-email-dwmw@amazon.co.uk> (raw)
In-Reply-To: <1517070274-12128-1-git-send-email-dwmw@amazon.co.uk>

From: Borislav Petkov <bp@suse.de>

Make it all a function which does the WRMSR instead of having a hairy
inline asm.

[dwmw2: export it, fix CONFIG_RETPOLINE issues]
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 arch/x86/include/asm/nospec-branch.h | 13 ++++---------
 arch/x86/include/asm/processor.h     |  3 +++
 arch/x86/kernel/cpu/bugs.c           |  6 ++++++
 3 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index df4ececa..d15d471 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -164,15 +164,10 @@ static inline void vmexit_fill_RSB(void)
 
 static inline void indirect_branch_prediction_barrier(void)
 {
-	asm volatile(ALTERNATIVE("",
-				 "movl %[msr], %%ecx\n\t"
-				 "movl %[val], %%eax\n\t"
-				 "movl $0, %%edx\n\t"
-				 "wrmsr",
-				 X86_FEATURE_USE_IBPB)
-		     : : [msr] "i" (MSR_IA32_PRED_CMD),
-			 [val] "i" (PRED_CMD_IBPB)
-		     : "eax", "ecx", "edx", "memory");
+	alternative_input("",
+			  "call __ibp_barrier",
+			  X86_FEATURE_USE_IBPB,
+			  ASM_NO_INPUT_CLOBBER("eax", "ecx", "edx", "memory"));
 }
 
 #endif /* __ASSEMBLY__ */
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 9c18da6..881ca3b 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -970,4 +970,7 @@ bool xen_set_default_idle(void);
 
 void stop_this_cpu(void *dummy);
 void df_debug(struct pt_regs *regs, long error_code);
+
+void __ibp_barrier(void);
+
 #endif /* _ASM_X86_PROCESSOR_H */
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 0c6dd43..dd99808 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -303,3 +303,9 @@ ssize_t cpu_show_spectre_v2(struct device *dev,
 		       spectre_v2_bad_module ? " - vulnerable module loaded" : "");
 }
 #endif
+
+void __ibp_barrier(void)
+{
+	__wrmsr(MSR_IA32_PRED_CMD, PRED_CMD_IBPB, 0);
+}
+EXPORT_SYMBOL_GPL(__ibp_barrier);
-- 
2.7.4

  parent reply	other threads:[~2018-01-27 16:24 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-27 16:24 [PATCH 0/3] Speculation CPU feature cleanups David Woodhouse
2018-01-27 16:24 ` [PATCH 1/3] x86/cpufeatures: Clean up Spectre v2 related CPUID flags David Woodhouse
2018-01-27 18:16   ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-27 16:24 ` [PATCH 2/3] x86/retpoline: Simplify vmexit_fill_RSB() David Woodhouse
2018-01-27 18:16   ` [tip:x86/pti] " tip-bot for Borislav Petkov
2018-01-27 16:24 ` David Woodhouse [this message]
2018-01-27 18:17   ` [tip:x86/pti] x86/speculation: Simplify indirect_branch_prediction_barrier() tip-bot for Borislav Petkov

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