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From: Alexey Makhalov <amakhalov@vmware.com>
To: <corbet@lwn.net>, <akataria@vmware.com>, <tglx@linutronix.de>,
	<mingo@redhat.com>, <hpa@zytor.com>, <x86@kernel.org>
Cc: <linux-doc@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<virtualization@lists.linux-foundation.org>,
	<pv-drivers@vmware.com>, Alexey Makhalov <amakhalov@vmware.com>
Subject: [RESEND PATCH 1/3] x86/vmware: Use tsc_khz value for calibrate_cpu()
Date: Thu, 27 Oct 2016 12:44:52 -0700	[thread overview]
Message-ID: <20161027194454.9729-1-amakhalov@vmware.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1610262247030.5013@nanos>

After aa297292d708, there are separate native calibrations for cpu_khz and
tsc_khz. The code sets x86_platform.calibrate_cpu to native_calibrate_cpu()
which looks in cpuid leaf 0x16 or msrs for the cpu frequency. Since we keep
the tsc_khz constant (even after vmotion), the cpu_khz and tsc_khz may
start diverging.

tsc_init() now does

	cpu_khz = x86_platform.calibrate_cpu();
	tsc_khz = x86_platform.calibrate_tsc();
	if (tsc_khz == 0)
		tsc_khz = cpu_khz;
	else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz)
		cpu_khz = tsc_khz;

We want the cpu_khz and tsc_khz to be sync even if they diverge less then
10%.
This patch resolves this issue by setting x86_platform.calibrate_cpu to
vmware_get_tsc_khz().

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Acked-by: Alok N Kataria <akataria@vmware.com>
---
 arch/x86/kernel/cpu/vmware.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 4e34da4b..480790f 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -83,6 +83,7 @@ static void __init vmware_platform_setup(void)
 
 		vmware_tsc_khz = tsc_khz;
 		x86_platform.calibrate_tsc = vmware_get_tsc_khz;
+		x86_platform.calibrate_cpu = vmware_get_tsc_khz;
 
 #ifdef CONFIG_X86_LOCAL_APIC
 		/* Skip lapic calibration since we know the bus frequency. */
-- 
2.10.1

  reply	other threads:[~2016-10-27 19:45 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-10-26  5:20 [PATCH 0/3] x86/vmware guest improvements Alexey Makhalov
2016-10-26  5:20 ` [PATCH 1/3] x86/vmware: Use tsc_khz value for calibrate_cpu() Alexey Makhalov
2016-10-26  5:26 ` [PATCH 2/3] x86/vmware: Add basic paravirt ops support Alexey Makhalov
2016-10-26 20:47   ` Tim Mann
2016-10-26 20:47     ` Thomas Gleixner
2016-10-27 19:44       ` Alexey Makhalov [this message]
2016-10-27 19:44         ` [RESEND PATCH " Alexey Makhalov
2016-10-27 19:44         ` [RESEND PATCH 3/3] x86/vmware: Add paravirt sched clock Alexey Makhalov
2016-10-27 22:10           ` Thomas Gleixner
2016-10-27 21:44         ` [RESEND PATCH 1/3] x86/vmware: Use tsc_khz value for calibrate_cpu() Thomas Gleixner
2016-10-28  7:54           ` [PATCH v3 0/3] x86/vmware guest improvements Alexey Makhalov
2016-10-28  7:54             ` [PATCH v3 1/3] x86/vmware: Use tsc_khz value for calibrate_cpu() Alexey Makhalov
2016-10-31  1:17               ` [tip:x86/platform] " tip-bot for Alexey Makhalov
2016-10-28  7:54             ` [PATCH v3 2/3] x86/vmware: Add basic paravirt ops support Alexey Makhalov
2016-10-31  1:17               ` [tip:x86/platform] " tip-bot for Alexey Makhalov
2016-10-28  7:54             ` [PATCH v3 3/3] x86/vmware: Add paravirt sched clock Alexey Makhalov
2016-10-31  1:18               ` [tip:x86/platform] " tip-bot for Alexey Makhalov
2016-10-26  5:26 ` [PATCH 3/3] " Alexey Makhalov
2016-10-26 10:18   ` Thomas Gleixner
2016-10-26 16:51     ` [PATCH v2 " Alexey Makhalov

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