linux-kernel - [PATCH v3 02/18] x86/msr/kvm: Remove vget

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Date:	Tue, 16 Jun 2015 17:35:50 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	x86@...nel.org
Cc:	Borislav Petkov <bp@...e.de>,
	Peter Zijlstra <peterz@...radead.org>,
	John Stultz <john.stultz@...aro.org>,
	linux-kernel@...r.kernel.org, Len Brown <lenb@...nel.org>,
	Huang Rui <ray.huang@....com>,
	Denys Vlasenko <dvlasenk@...hat.com>, kvm@...r.kernel.org,
	Ralf Baechle <ralf@...ux-mips.org>,
	Andy Lutomirski <luto@...nel.org>
Subject: [PATCH v3 02/18] x86/msr/kvm: Remove vget_cycles()

The only caller was kvm's read_tsc.  The only difference between
vget_cycles and native_read_tsc was that vget_cycles returned zero
instead of crashing on TSC-less systems.  KVM's already checks
vclock_mode before calling that function, so the extra check is
unnecessary.

(Off-topic, but the whole KVM clock host implementation is gross.
 IMO it should be rewritten.)

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/include/asm/tsc.h | 13 -------------
 arch/x86/kvm/x86.c         |  2 +-
 2 files changed, 1 insertion(+), 14 deletions(-)

diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index fd11128faf25..3da1cc1218ac 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -32,19 +32,6 @@ static inline cycles_t get_cycles(void)
 	return ret;
 }
 
-static __always_inline cycles_t vget_cycles(void)
-{
-	/*
-	 * We only do VDSOs on TSC capable CPUs, so this shouldn't
-	 * access boot_cpu_data (which is not VDSO-safe):
-	 */
-#ifndef CONFIG_X86_TSC
-	if (!cpu_has_tsc)
-		return 0;
-#endif
-	return (cycles_t)native_read_tsc();
-}
-
 extern void tsc_init(void);
 extern void mark_tsc_unstable(char *reason);
 extern int unsynchronized_tsc(void);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 26eaeb522cab..c26faf408bce 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1430,7 +1430,7 @@ static cycle_t read_tsc(void)
 	 * but no one has ever seen it happen.
 	 */
 	rdtsc_barrier();
-	ret = (cycle_t)vget_cycles();
+	ret = (cycle_t)native_read_tsc();
 
 	last = pvclock_gtod_data.clock.cycle_last;
 
-- 
2.4.2

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