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Commit d72f4e29 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

x86/speculation: Move firmware_restrict_branch_speculation_*() from C to CPP 



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: default avatarIngo Molnar <mingo@kernel.org>
parent ca41b97e

arch/x86/include/asm/nospec-branch.h

+14 −12
Original line number Diff line number Diff line
@@ -257,20 +257,22 @@ 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__ */

#endif /* _ASM_X86_NOSPEC_BRANCH_H_ */