| Message ID | 1580830825-18767-3-git-send-email-igor.druzhinin@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | PV shim timekeeping fixes | expand |
On Tue, Feb 04, 2020 at 03:40:25PM +0000, Igor Druzhinin wrote: > The value of the counter represents the number of nanoseconds > since host boot. That means the correct frequency is always 1GHz. > > This inconsistency caused time to go slower in PV shim on most > platforms. > > Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com> Reviewed-by: Roger Pau Monné <roger.pau@citrix.com> With one nit below. > --- > xen/arch/x86/time.c | 17 +---------------- > 1 file changed, 1 insertion(+), 16 deletions(-) > > diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c > index 7e7a62e..95840c4 100644 > --- a/xen/arch/x86/time.c > +++ b/xen/arch/x86/time.c > @@ -567,27 +567,12 @@ static struct platform_timesource __initdata plt_tsc = > */ > static uint64_t xen_timer_last; > > -static uint64_t xen_timer_cpu_frequency(void) > -{ > - struct vcpu_time_info *info = &this_cpu(vcpu_info)->time; > - uint64_t freq; > - > - freq = 1000000000ULL << 32; > - do_div(freq, info->tsc_to_system_mul); > - if ( info->tsc_shift < 0 ) > - freq <<= -info->tsc_shift; > - else > - freq >>= info->tsc_shift; > - > - return freq; > -} > - > static int64_t __init init_xen_timer(struct platform_timesource *pts) > { > if ( !xen_guest ) > return 0; > > - pts->frequency = xen_timer_cpu_frequency(); > + pts->frequency = 1000000000ULL; You can init this field below at declaration, since it's a static value. Thanks, Roger.
On 04/02/2020 17:28, Roger Pau Monné wrote: > On Tue, Feb 04, 2020 at 03:40:25PM +0000, Igor Druzhinin wrote: >> The value of the counter represents the number of nanoseconds >> since host boot. That means the correct frequency is always 1GHz. >> >> This inconsistency caused time to go slower in PV shim on most >> platforms. >> >> Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com> > > Reviewed-by: Roger Pau Monné <roger.pau@citrix.com> Actually, this patch is buggy and causes a system to always detect 1GHz processor. I'll send a v2. Igor
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c index 7e7a62e..95840c4 100644 --- a/xen/arch/x86/time.c +++ b/xen/arch/x86/time.c @@ -567,27 +567,12 @@ static struct platform_timesource __initdata plt_tsc = */ static uint64_t xen_timer_last; -static uint64_t xen_timer_cpu_frequency(void) -{ - struct vcpu_time_info *info = &this_cpu(vcpu_info)->time; - uint64_t freq; - - freq = 1000000000ULL << 32; - do_div(freq, info->tsc_to_system_mul); - if ( info->tsc_shift < 0 ) - freq <<= -info->tsc_shift; - else - freq >>= info->tsc_shift; - - return freq; -} - static int64_t __init init_xen_timer(struct platform_timesource *pts) { if ( !xen_guest ) return 0; - pts->frequency = xen_timer_cpu_frequency(); + pts->frequency = 1000000000ULL; return pts->frequency; }
The value of the counter represents the number of nanoseconds since host boot. That means the correct frequency is always 1GHz. This inconsistency caused time to go slower in PV shim on most platforms. Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com> --- xen/arch/x86/time.c | 17 +---------------- 1 file changed, 1 insertion(+), 16 deletions(-)