linux-kernel - [PATCH 14/24] x86/speculation: Move firmware_restrict_branch_speculation

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Message-Id: <1523939240-16508-14-git-send-email-youquan.song@intel.com>
Date:   Tue, 17 Apr 2018 00:27:10 -0400
From:   Youquan Song <youquan.song@...el.com>
To:     stable@...r.kernel.org, gregkh@...uxfoundation.org
Cc:     tim.c.chen@...ux.intel.com, ashok.raj@...el.com,
        dave.hansen@...el.com, yi.y.sun@...ux.intel.com,
        youquan.song@...el.com, youquan.song@...ux.intel.com,
        Ingo Molnar <mingo@...nel.org>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        arjan.van.de.ven@...el.com, bp@...en8.de, jmattson@...gle.com,
        karahmed@...zon.de, kvm@...r.kernel.org, pbonzini@...hat.com,
        rkrcmar@...hat.com, linux-kernel@...r.kernel.org
Subject: [PATCH 14/24] x86/speculation: Move firmware_restrict_branch_speculation_*() from C to CPP

From: Ingo Molnar <mingo@...nel.org>

(cherry picked from commit d72f4e29e6d84b7ec02ae93088aa459ac70e733b)

firmware_restrict_branch_speculation_*() recently started using
preempt_enable()/disable(), but those are relatively high level
primitives and cause build failures on some 32-bit builds.

Since we want to keep <asm/nospec-branch.h> low level, convert
them to macros to avoid header hell...

Cc: David Woodhouse <dwmw@...zon.co.uk>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: arjan.van.de.ven@...el.com
Cc: bp@...en8.de
Cc: dave.hansen@...el.com
Cc: jmattson@...gle.com
Cc: karahmed@...zon.de
Cc: kvm@...r.kernel.org
Cc: pbonzini@...hat.com
Cc: rkrcmar@...hat.com
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Youquan Song <youquan.song@...ux.intel.com> [v4.4 backport]
---
 arch/x86/include/asm/nospec-branch.h | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 27582aa..4675f65 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -214,20 +214,22 @@ static inline void indirect_branch_prediction_barrier(void)
 /*
  * With retpoline, we must use IBRS to restrict branch prediction
  * before calling into firmware.
+ *
+ * (Implemented as CPP macros due to header hell.)
  */
-static inline void firmware_restrict_branch_speculation_start(void)
-{
-	preempt_disable();
-	alternative_msr_write(MSR_IA32_SPEC_CTRL, SPEC_CTRL_IBRS,
-			      X86_FEATURE_USE_IBRS_FW);
-}
+#define firmware_restrict_branch_speculation_start()			\
+do {									\
+	preempt_disable();						\
+	alternative_msr_write(MSR_IA32_SPEC_CTRL, SPEC_CTRL_IBRS,	\
+			      X86_FEATURE_USE_IBRS_FW);			\
+} while (0)
 
-static inline void firmware_restrict_branch_speculation_end(void)
-{
-	alternative_msr_write(MSR_IA32_SPEC_CTRL, 0,
-			      X86_FEATURE_USE_IBRS_FW);
-	preempt_enable();
-}
+#define firmware_restrict_branch_speculation_end()			\
+do {									\
+	alternative_msr_write(MSR_IA32_SPEC_CTRL, 0,			\
+			      X86_FEATURE_USE_IBRS_FW);			\
+	preempt_enable();						\
+} while (0)
 
 #endif /* __ASSEMBLY__ */
 
-- 
1.8.3.1