[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v3 02/13] x86/time.c: Use correct guest TSC frequency in tsc_get_info()
On 01/08/16 02:05, Jan Beulich wrote: > >>> On 04.01.16 at 18:48, <boris.ostrovsky@xxxxxxxxxx> wrote: > > On 12/30/2015 10:03 PM, Haozhong Zhang wrote: > >> When the TSC mode of a HVM container is TSC_MODE_DEFAULT or > >> TSC_MODE_PVRDTSCP and no TSC emulation is used, the existing > >> tsc_get_info() uses the host TSC frequency (cpu_khz) as the guest TSC > >> frequency. However, tsc_set_info() may set the guest TSC frequency to a > >> value different than the host. In order to keep consistent to > >> tsc_set_info(), this patch makes tsc_get_info() use the value set by > >> tsc_set_info() as the guest TSC frequency. > >> > >> Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx> > >> --- > >> Changes in v3: > >> (addressing Boris Ostrovsky's comments) > >> * Use this_cpu(cpu_time).tsc_scale for both scaling and non-scaling > >> cases. > >> > >> xen/arch/x86/time.c | 9 ++++++--- > >> 1 file changed, 6 insertions(+), 3 deletions(-) > >> > >> diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c > >> index 0059b6a..d83f068 100644 > >> --- a/xen/arch/x86/time.c > >> +++ b/xen/arch/x86/time.c > >> @@ -1749,6 +1749,9 @@ void tsc_get_info(struct domain *d, uint32_t > >> *tsc_mode, > >> uint64_t *elapsed_nsec, uint32_t *gtsc_khz, > >> uint32_t *incarnation) > >> { > >> + bool_t enable_tsc_scaling = has_hvm_container_domain(d) && > >> + cpu_has_tsc_ratio; > >> + > > > > Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> > > > > although I still think that having !d->arch.vtsc would be better, even > > if not strictly required. > > Since Haozhong agreed, and for symmetry with patch 1 I'm going to > commit with this added, plus ... > > >> @@ -1780,9 +1783,9 @@ void tsc_get_info(struct domain *d, uint32_t > >> *tsc_mode, > >> else > >> { > >> tsc = rdtsc(); > >> - *elapsed_nsec = scale_delta(tsc, &d->arch.vtsc_to_ns) - > >> + *elapsed_nsec = scale_delta(tsc, > >> &this_cpu(cpu_time).tsc_scale) - > >> d->arch.vtsc_offset; > >> - *gtsc_khz = 0; /* ignored by tsc_set_info */ > >> + *gtsc_khz = enable_tsc_scaling ? d->arch.tsc_khz : 0; > > ... with the comment here retained. > And it's better to refine the comment like /* ignored by tsc_set_info if TSC scaling disabled */ Haozhong _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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