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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, David Woodhouse <dwmw@amazon.co.uk>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        arjan.van.de.ven@intel.com, bp@alien8.de, dave.hansen@intel.com,
        jmattson@google.com, karahmed@amazon.de, kvm@vger.kernel.org,
        pbonzini@redhat.com, rkrcmar@redhat.com,
        Ingo Molnar <mingo@kernel.org>
Subject: [PATCH 4.14 127/140] x86/speculation: Move firmware_restrict_branch_speculation_*() from C to CPP
Date:   Tue, 13 Mar 2018 16:25:30 +0100
Message-Id: <20180313152506.718774430@linuxfoundation.org>
In-Reply-To: <20180313152458.201155692@linuxfoundation.org>
References: <20180313152458.201155692@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ingo Molnar <mingo@kernel.org>

commit d72f4e29e6d84b7ec02ae93088aa459ac70e733b upstream.

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@amazon.co.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: arjan.van.de.ven@intel.com
Cc: bp@alien8.de
Cc: dave.hansen@intel.com
Cc: jmattson@google.com
Cc: karahmed@amazon.de
Cc: kvm@vger.kernel.org
Cc: pbonzini@redhat.com
Cc: rkrcmar@redhat.com
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/include/asm/nospec-branch.h |   26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -257,20 +257,22 @@ static inline void indirect_branch_predi
 /*
  * 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__ */