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xen-devel
RE: [Xen-devel] [PATCH] TSC scaling for live migration betweenplatforms
Jan Beulich wrote:
>>>> "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx> 18.06.09 04:56 >>>
>> PATCH 0003-- Scaling host TSC freqeuncy patch.
>
>> +int hvm_gtsc_need_scale(struct domain *d)
>> +{
>> + uint32_t gtsc_khz;
>> +
>> + gtsc_khz = d->arch.hvm_domain.gtsc_khz / 1000;
>
> Can the variable please be renamed to what it contains (i.e.
> gtsc_mhz)?
>
>> u64 hvm_get_guest_tsc(struct vcpu *v)
>> {
>> - u64 host_tsc;
>> -
>> - if ( opt_softtsc )
>> - host_tsc = hvm_get_guest_time(v);
>> - else
>> - rdtscll(host_tsc);
>> -
>> - return host_tsc + v->arch.hvm_vcpu.cache_tsc_offset;
>> + u64 host_tsc, scaled_htsc;
>> +
>> + rdtscll(host_tsc);
>> + scaled_htsc = hvm_h2g_scale_tsc(v, host_tsc);
>> +
>> + return scaled_htsc + v->arch.hvm_vcpu.cache_tsc_offset; }
>>
>> void hvm_migrate_timers(struct vcpu *v)
>
> I'm getting the impression that the opt_softtsc functionality got
> lost here.
I am still confused by opt_softtsc check here. If want to use platform timer to
emulate guest's tsc, hvm_set_guest_tsc should also need perform this check to
get correct cache_tsc_offset, but I didn't see it. A bug ?
If use host's tsc to emulate guest's tsc, the check is useless, so I removed it
in my patch. Maybe we need Dan's explanation about the check here to determin
whether keep it or not.
>
>> + printk("Migrate to a platform with different freq:%ldMhz, "
>> + "expected freq:%dMhz, enable rdtsc exiting!\n",
>> + cpu_khz / 1000, hdr->gtsc_khz / 1000);
>
> gdprintk()? At least, I think, any guest related printk-s should
> identify which guest they're about.
Added in the attached patch. Thanks!
Xiantao
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