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From: "K. Y. Srinivasan" <kys@microsoft.com>
To: x86@kernel.org, gregkh@linuxfoundation.org,
	linux-kernel@vger.kernel.org, devel@linuxdriverproject.org,
	olaf@aepfle.de, apw@canonical.com, jasowang@redhat.com,
	tglx@linutronix.de, hpa@zytor.com, JBeulich@suse.com,
	bp@alien8.de
Cc: Olaf Hering <"[mailto:olaf@aepfle.de]"@linuxonhyperv.com>,
	"K. Y. Srinivasan" <kys@microsoft.com>,
	stable@kernel.org
Subject: [PATCH 1/3] x86: Hyper-V: register clocksource only if its advertised
Date: Tue, 29 Jan 2013 16:51:46 -0800	[thread overview]
Message-ID: <1359507108-26091-1-git-send-email-kys@microsoft.com> (raw)
In-Reply-To: <1359507077-26050-1-git-send-email-kys@microsoft.com>

From: Olaf Hering <[mailto:olaf@aepfle.de]>

Enable hyperv_clocksource only if its advertised as a feature.
XenServer 6 returns the signature which is checked in
ms_hyperv_platform(), but it does not offer all features. Currently the
clocksource is enabled unconditionally in ms_hyperv_init_platform(), and
the result is a hanging guest.

Hyper-V spec Bit 1 indicates the availability of Partition Reference
Counter.  Register the clocksource only if this bit is set.

The guest in question prints this in dmesg:
 [    0.000000] Hypervisor detected: Microsoft HyperV
 [    0.000000] HyperV: features 0x70, hints 0x0

This bug can be reproduced easily be setting 'viridian=1' in a HVM domU
.cfg file. A workaround without this patch is to boot the HVM guest with
'clocksource=jiffies'.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Cc: stable@kernel.org
Cc: Greg KH <gregkh@linuxfoundation.org>
---
 arch/x86/kernel/cpu/mshyperv.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 0a630dd..646d192 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -68,7 +68,8 @@ static void __init ms_hyperv_init_platform(void)
 	printk(KERN_INFO "HyperV: features 0x%x, hints 0x%x\n",
 	       ms_hyperv.features, ms_hyperv.hints);
 
-	clocksource_register_hz(&hyperv_cs, NSEC_PER_SEC/100);
+	if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
+		clocksource_register_hz(&hyperv_cs, NSEC_PER_SEC/100);
 }
 
 const __refconst struct hypervisor_x86 x86_hyper_ms_hyperv = {
-- 
1.7.4.1


  reply	other threads:[~2013-01-30  0:24 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-01-30  0:51 [PATCH 0/3] X86: Deliver Hyper-V interrupts on a seperate IDT vector K. Y. Srinivasan
2013-01-30  0:51 ` K. Y. Srinivasan [this message]
2013-01-30  0:51   ` [PATCH 2/3] X86: Add a check to catch Xen emulation of Hyper-V K. Y. Srinivasan
2013-01-30  8:53     ` Jan Beulich
2013-01-30 18:12       ` KY Srinivasan
2013-01-30 18:19         ` H. Peter Anvin
2013-01-31  7:37         ` Jan Beulich
2013-01-31 14:46           ` KY Srinivasan
2013-01-31 15:53             ` KY Srinivasan
2013-01-31 16:45               ` Jan Beulich
2013-01-31 18:29                 ` H. Peter Anvin
2013-01-31 21:41       ` H. Peter Anvin
2013-02-01 13:19         ` Stefano Stabellini
2013-02-01 15:10           ` KY Srinivasan
2013-02-01 19:34             ` KY Srinivasan
2013-01-30  0:51   ` [PATCH 3/3] X86: Handle Hyper-V vmbus interrupts as special hypervisor interrupts K. Y. Srinivasan
2013-01-30  8:58     ` Jan Beulich
2013-01-31 14:55       ` KY Srinivasan
2013-02-04  1:21 [PATCH 0/3] X86: Deliver Hyper-V interrupts on a seperate IDT vector K. Y. Srinivasan
2013-02-04  1:22 ` [PATCH 1/3] x86: Hyper-V: register clocksource only if its advertised K. Y. Srinivasan

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