> -----Original Message----- > From: Dexuan Cui > Sent: Monday, July 20, 2015 5:14 AM > To: KY Srinivasan; gregkh@xxxxxxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx; > apw@xxxxxxxxxxxxx; vkuznets@xxxxxxxxxx; jasowang@xxxxxxxxxx > 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 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
