x86/asm: Fix MWAITX C-state hint value (454de1e7) · Commits · 戴 / test

As per "AMD64 Architecture Programmer's Manual Volume 3: General-Purpose and System Instructions", MWAITX EAX[7:4]+1 specifies the optional hint of the optimized C-state. For C0 state, EAX[7:4] should be set to 0xf. Currently, a value of 0xf is set for EAX[3:0] instead of EAX[7:4]. Fix this by changing MWAITX_DISABLE_CSTATES from 0xf to 0xf0. This hasn't had any implications so far because setting reserved bits in EAX is simply ignored by the CPU. [ bp: Fixup comment in delay_mwaitx() and massage. ] Signed-off-by:

Janakarajan Natarajan <Janakarajan.Natarajan@amd.com> Signed-off-by:

Borislav Petkov <bp@suse.de> Cc: Frederic Weisbecker <frederic@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "x86@kernel.org" <x86@kernel.org> Cc: Zhenzhong Duan <zhenzhong.duan@oracle.com> Cc: <stable@vger.kernel.org> Link: https://lkml.kernel.org/r/20191007190011.4859-1-Janakarajan.Natarajan@amd.com Signed-off-by:

Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/mwait.h

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -21,7 +21,7 @@
	#define MWAIT_ECX_INTERRUPT_BREAK 0x1		#define MWAIT_ECX_INTERRUPT_BREAK 0x1
	#define MWAITX_ECX_TIMER_ENABLE BIT(1)		#define MWAITX_ECX_TIMER_ENABLE BIT(1)
	#define MWAITX_MAX_LOOPS ((u32)-1)		#define MWAITX_MAX_LOOPS ((u32)-1)
	#define MWAITX_DISABLE_CSTATES 0xf		#define MWAITX_DISABLE_CSTATES 0xf0

	static inline void __monitor(const void *eax, unsigned long ecx,		static inline void __monitor(const void *eax, unsigned long ecx,
	unsigned long edx)		unsigned long edx)

arch/x86/lib/delay.c

+2 −2

Original line number	Original line	Diff line number	Diff line
	@@ -113,8 +113,8 @@ static void delay_mwaitx(unsigned long __loops)
	__monitorx(raw_cpu_ptr(&cpu_tss_rw), 0, 0);		__monitorx(raw_cpu_ptr(&cpu_tss_rw), 0, 0);

	/*		/*
	* AMD, like Intel, supports the EAX hint and EAX=0xf		* AMD, like Intel's MWAIT version, supports the EAX hint and
	* means, do not enter any deep C-state and we use it		* EAX=0xf0 means, do not enter any deep C-state and we use it
	* here in delay() to minimize wakeup latency.		* here in delay() to minimize wakeup latency.
	*/		*/
	__mwaitx(MWAITX_DISABLE_CSTATES, delay, MWAITX_ECX_TIMER_ENABLE);		__mwaitx(MWAITX_DISABLE_CSTATES, delay, MWAITX_ECX_TIMER_ENABLE);

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