[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v4 1/3] x86: Use native RDTSC(P) execution when guest and host frequencies are the same
On 04/16/2014 05:54 AM, Jan Beulich wrote: On 16.04.14 at 03:27, <boris.ostrovsky@xxxxxxxxxx> wrote:@@ -1889,10 +1890,14 @@ void tsc_set_info(struct domain *d, d->arch.vtsc_offset = get_s_time() - elapsed_nsec; d->arch.tsc_khz = gtsc_khz ? gtsc_khz : cpu_khz; set_time_scale(&d->arch.vtsc_to_ns, d->arch.tsc_khz * 1000 ); - /* use native TSC if initial host has safe TSC, has not migrated - * yet and tsc_khz == cpu_khz */ - if ( host_tsc_is_safe() && incarnation == 0 && - d->arch.tsc_khz == cpu_khz ) + /* + * Use native TSC if initial host has safe TSC and either has not + * migrated yet or tsc_khz == cpu_khz (either "naturally" or via + * TSC scaling) + */ + if ( host_tsc_is_safe() && + (incarnation == 0 || d->arch.tsc_khz == cpu_khz || + cpu_has_tsc_ratio) )Can't you drop checking incarnation to be zero then? In that case, afaict d->arch.tsc_khz == cpu_khz due to gtsc_khz being passed in as zero from arch_domain_create(). Yes, it's pointless. I was thinking that maybe toolstack may pass gtsc_khz != cpu_khz during initial boot (it doesn't do it now, but theoretically it could) but then we shouldn't be using vtsc=0 in that case anyway. -boris _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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