[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] x86/time: Don't use virtual TSC if host and guest frequencies are equal
On 03/16/2017 06:40 AM, Jan Beulich wrote: >>>> On 15.03.17 at 20:48, <boris.ostrovsky@xxxxxxxxxx> wrote: >> --- a/xen/arch/x86/time.c >> +++ b/xen/arch/x86/time.c >> @@ -2051,17 +2051,11 @@ void tsc_set_info(struct domain *d, >> d->arch.vtsc_offset = get_s_time() - elapsed_nsec; >> d->arch.tsc_khz = gtsc_khz ?: cpu_khz; >> set_time_scale(&d->arch.vtsc_to_ns, d->arch.tsc_khz * 1000); >> - /* >> - * In default mode use native TSC if the host has safe TSC and: >> - * HVM/PVH: host and guest frequencies are the same (either >> - * "naturally" or via TSC scaling) >> - * PV: guest has not migrated yet (and thus arch.tsc_khz == >> cpu_khz) >> - */ >> + >> if ( tsc_mode == TSC_MODE_DEFAULT && host_tsc_is_safe() && >> - (has_hvm_container_domain(d) ? >> - (d->arch.tsc_khz == cpu_khz || >> - hvm_get_tsc_scaling_ratio(d->arch.tsc_khz)) : >> - incarnation == 0) ) >> + (d->arch.tsc_khz == cpu_khz || incarnation == 0 || > Is the incarnation comparison really needed here, i.e. doesn't it > being zero imply the two frequencies to match in default mode? It is not necessary but I wanted to keep it for clarity so that it is explicit that when a domain is born we don't use vtsc. -boris _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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