[3.8.y.z extended stable] Patch "x86, hyperv: Bypass the timer_irq_works() check" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    x86, hyperv: Bypass the timer_irq_works() check

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.22.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 8e4a48ca85b84dc4525c81f1c36ac209ab92d79e Mon Sep 17 00:00:00 2001
From: Jason Wang <jasowang at redhat.com>
Date: Fri, 28 Feb 2014 11:30:29 +0800
Subject: x86, hyperv: Bypass the timer_irq_works() check

commit ca3ba2a2f4a49a308e7d78c784d51b2332064f15 upstream.

This patch bypass the timer_irq_works() check for hyperv guest since:

- It was guaranteed to work.
- timer_irq_works() may fail sometime due to the lpj calibration were inaccurate
  in a hyperv guest or a buggy host.

In the future, we should get the tsc frequency from hypervisor and use preset
lpj instead.

[ hpa: I would prefer to not defer things to "the future" in the future... ]

Cc: K. Y. Srinivasan <kys at microsoft.com>
Cc: Haiyang Zhang <haiyangz at microsoft.com>
Acked-by: K. Y. Srinivasan <kys at microsoft.com>
Signed-off-by: Jason Wang <jasowang at redhat.com>
Link: http://lkml.kernel.org/r/1393558229-14755-1-git-send-email-jasowang@redhat.com
Signed-off-by: H. Peter Anvin <hpa at linux.intel.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/x86/kernel/cpu/mshyperv.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 646d192..1a3cf6e 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -18,6 +18,7 @@
 #include <asm/hypervisor.h>
 #include <asm/hyperv.h>
 #include <asm/mshyperv.h>
+#include <asm/timer.h>

 struct ms_hyperv_info ms_hyperv;
 EXPORT_SYMBOL_GPL(ms_hyperv);
@@ -70,6 +71,11 @@ static void __init ms_hyperv_init_platform(void)

 	if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
 		clocksource_register_hz(&hyperv_cs, NSEC_PER_SEC/100);
+
+#ifdef CONFIG_X86_IO_APIC
+	no_timer_check = 1;
+#endif
+
 }

 const __refconst struct hypervisor_x86 x86_hyper_ms_hyperv = {
--
1.9.1