lkml.org 
[lkml]   [2015]   [Jul]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRE: [PATCH 5/5] Drivers: hv: vmbus: Implement a clocksource based on the TSC page
Date


> -----Original Message-----
> From: Dexuan Cui
> Sent: Monday, July 20, 2015 5:14 AM
> To: KY Srinivasan; gregkh@linuxfoundation.org; linux-
> kernel@vger.kernel.org; devel@linuxdriverproject.org; olaf@aepfle.de;
> apw@canonical.com; vkuznets@redhat.com; jasowang@redhat.com
> Subject: RE: [PATCH 5/5] Drivers: hv: vmbus: Implement a clocksource based
> on the TSC page
>
> > From: devel [mailto:driverdev-devel-bounces...linuxdriverproject.org] On
> Behalf
> > Of K. Y. Srinivasan
> > Sent: Monday, July 20, 2015 11:37
> >
> > The current Hyper-V clock source is based on the per-partition reference
> counter
> > and this counter is being accessed via s synthetic MSR -
> > HV_X64_MSR_TIME_REF_COUNT.
> > Hyper-V has a more efficient way of computing the per-partition reference
> > counter value that does not involve reading a synthetic MSR. We
> implement
> > a time source based on this mechanism.
> > ...
> > diff --git a/arch/x86/include/uapi/asm/hyperv.h
> > @@ -183,6 +233,22 @@ int hv_init(void)
> >
> > hv_context.hypercall_page = virtaddr;
> >
> > +#ifdef CONFIG_X86_64
> > + if (ms_hyperv.features &
> HV_X64_MSR_REFERENCE_TSC_AVAILABLE) {
> > + va_tsc = __vmalloc(PAGE_SIZE, GFP_KERNEL,
> PAGE_KERNEL);
> > + if (!va_tsc)
> > + goto cleanup;
> > + hv_context.tsc_page = va_tsc;
> > +
> > + rdmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
> > +
> > + tsc_msr.enable = 1;
> > + tsc_msr.guest_physical_address = vmalloc_to_pfn(va_tsc);
> > +
> > + wrmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
> > + clocksource_register_hz(&hyperv_cs_tsc,
> NSEC_PER_SEC/100);
> > + }
> > +#endif
>
> Should we disable the mechanism and vfree() the page in hv_cleanup() for
> kexec/kdump?

Thanks Dexuan. I will update the patch and resend.

Regards,

K. Y
>
> -- Dexuan


\
 
 \ /
  Last update: 2015-07-20 21:21    [W:0.109 / U:1.232 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site