> 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? -- Dexuan _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
