similar to: [PATCH 0/2] x86/vdso: Add Hyper-V TSC page clocksource support

Hi, merge window is about to close so I hope it's OK to make another try here. Changes since v2: - Add explicit READ_ONCE() to not rely on 'volatile' [Andy Lutomirski] - rdtsc() -> rdtsc_ordered() [Andy Lutomirski] - virt_rmb() -> smp_rmb() [Thomas Gleixner, Andy Lutomirski] Thomas, Andy, it seems the only blocker for the series was the ambiguity with TSC page read algorithm.

Hi, merge window is about to close so I hope it's OK to make another try here. Changes since v2: - Add explicit READ_ONCE() to not rely on 'volatile' [Andy Lutomirski] - rdtsc() -> rdtsc_ordered() [Andy Lutomirski] - virt_rmb() -> smp_rmb() [Thomas Gleixner, Andy Lutomirski] Thomas, Andy, it seems the only blocker for the series was the ambiguity with TSC page read algorithm.

Hi, while we're still waiting for a definitive ACK from Microsoft that the algorithm is good for SMP case (as we can't prevent the code in vdso from migrating between CPUs) I'd like to send v2 with some modifications to keep the discussion going. Changes since v1: - Document the TSC page reading protocol [Thomas Gleixner]. - Separate the TSC page reading code from

Hi, while we're still waiting for a definitive ACK from Microsoft that the algorithm is good for SMP case (as we can't prevent the code in vdso from migrating between CPUs) I'd like to send v2 with some modifications to keep the discussion going. Changes since v1: - Document the TSC page reading protocol [Thomas Gleixner]. - Separate the TSC page reading code from

Hi, Hyper-V TSC page clocksource is suitable for vDSO, however, the protocol defined by the hypervisor is different from VCLOCK_PVCLOCK. I implemented the required support re-using pvclock_page VVAR. Simple sysbench test shows the following results: Before: # time sysbench --test=memory --max-requests=500000 run ... real 1m22.618s user 0m50.193s sys 0m32.268s After: # time sysbench

Hi, Hyper-V TSC page clocksource is suitable for vDSO, however, the protocol defined by the hypervisor is different from VCLOCK_PVCLOCK. I implemented the required support re-using pvclock_page VVAR. Simple sysbench test shows the following results: Before: # time sysbench --test=memory --max-requests=500000 run ... real 1m22.618s user 0m50.193s sys 0m32.268s After: # time sysbench

On Thu, 9 Feb 2017, Vitaly Kuznetsov wrote: > +#ifdef CONFIG_HYPERV_TSCPAGE > +static notrace u64 vread_hvclock(int *mode) > +{ > + const struct ms_hyperv_tsc_page *tsc_pg = > + (const struct ms_hyperv_tsc_page *)&hvclock_page; > + u64 sequence, scale, offset, current_tick, cur_tsc; > + > + while (1) { > + sequence = READ_ONCE(tsc_pg->tsc_sequence); > + if

On Thu, 9 Feb 2017, Vitaly Kuznetsov wrote: > +#ifdef CONFIG_HYPERV_TSCPAGE > +static notrace u64 vread_hvclock(int *mode) > +{ > + const struct ms_hyperv_tsc_page *tsc_pg = > + (const struct ms_hyperv_tsc_page *)&hvclock_page; > + u64 sequence, scale, offset, current_tick, cur_tsc; > + > + while (1) { > + sequence = READ_ONCE(tsc_pg->tsc_sequence); > + if

On Wed, Feb 8, 2017 at 9:07 AM, Vitaly Kuznetsov <vkuznets at redhat.com> wrote: > Hyper-V TSC page clocksource is suitable for vDSO, however, the protocol > defined by the hypervisor is different from VCLOCK_PVCLOCK. Implement the > required support re-using pvclock_page VVAR as VCLOCK_PVCLOCK is mutually > exclusive with VCLOCK_HVCLOCK at run time. > > Signed-off-by:

On Wed, Feb 8, 2017 at 9:07 AM, Vitaly Kuznetsov <vkuznets at redhat.com> wrote: > Hyper-V TSC page clocksource is suitable for vDSO, however, the protocol > defined by the hypervisor is different from VCLOCK_PVCLOCK. Implement the > required support re-using pvclock_page VVAR as VCLOCK_PVCLOCK is mutually > exclusive with VCLOCK_HVCLOCK at run time. > > Signed-off-by:

The actual code looks fine, but the style police will not like you. { should be at start of line on functions. And #else should be at start of line, But maybe this was just more of exchange mangling the mail. -----Original Message----- From: Vitaly Kuznetsov [mailto:vkuznets at redhat.com] Sent: Thursday, February 9, 2017 6:11 AM To: x86 at kernel.org; Andy Lutomirski <luto at

The actual code looks fine, but the style police will not like you. { should be at start of line on functions. And #else should be at start of line, But maybe this was just more of exchange mangling the mail. -----Original Message----- From: Vitaly Kuznetsov [mailto:vkuznets at redhat.com] Sent: Thursday, February 9, 2017 6:11 AM To: x86 at kernel.org; Andy Lutomirski <luto at

On Thu, Feb 9, 2017 at 12:45 PM, KY Srinivasan <kys at microsoft.com> wrote: > > >> -----Original Message----- >> From: Thomas Gleixner [mailto:tglx at linutronix.de] >> Sent: Thursday, February 9, 2017 9:08 AM >> To: Vitaly Kuznetsov <vkuznets at redhat.com> >> Cc: x86 at kernel.org; Andy Lutomirski <luto at amacapital.net>; Ingo Molnar

On Thu, Feb 9, 2017 at 12:45 PM, KY Srinivasan <kys at microsoft.com> wrote: > > >> -----Original Message----- >> From: Thomas Gleixner [mailto:tglx at linutronix.de] >> Sent: Thursday, February 9, 2017 9:08 AM >> To: Vitaly Kuznetsov <vkuznets at redhat.com> >> Cc: x86 at kernel.org; Andy Lutomirski <luto at amacapital.net>; Ingo Molnar

Hyper-V TSC page clocksource is suitable for vDSO, however, the protocol defined by the hypervisor is different from VCLOCK_PVCLOCK. Implement the required support by adding hvclock_page VVAR. Signed-off-by: Vitaly Kuznetsov <vkuznets at redhat.com> --- arch/x86/entry/vdso/vclock_gettime.c | 36 +++++++++++++++++++++++++++++++++++ arch/x86/entry/vdso/vdso-layout.lds.S | 3 ++-

Minor coding comments > diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h > index d324dce..4ff25436 100644 > --- a/arch/x86/include/asm/mshyperv.h > +++ b/arch/x86/include/asm/mshyperv.h > @@ -178,6 +178,56 @@ void hyperv_cleanup(void); > #endif > #ifdef CONFIG_HYPERV_TSCPAGE > struct ms_hyperv_tsc_page *hv_get_tsc_page(void); > +static

Minor coding comments > diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h > index d324dce..4ff25436 100644 > --- a/arch/x86/include/asm/mshyperv.h > +++ b/arch/x86/include/asm/mshyperv.h > @@ -178,6 +178,56 @@ void hyperv_cleanup(void); > #endif > #ifdef CONFIG_HYPERV_TSCPAGE > struct ms_hyperv_tsc_page *hv_get_tsc_page(void); > +static

As a preparation to making Hyper-V TSC page suitable for vDSO move the TSC page reading logic to asm/mshyperv.h. While on it, do the following - Document the reading algorithm. - Simplify the code a bit. - Add explicit READ_ONCE() to not rely on 'volatile'. - Add explicit barriers to prevent re-ordering (we need to read sequence strictly before and after) - Use mul_u64_u64_shr() instead

To use Hyper-V TSC page clocksource from vDSO we need to make tsc_pg available. Implement hv_get_tsc_page() and add CONFIG_HYPERV_TSCPAGE to make #ifdef-s simple. Signed-off-by: Vitaly Kuznetsov <vkuznets at redhat.com> --- arch/x86/hyperv/hv_init.c | 9 +++++++-- arch/x86/include/asm/mshyperv.h | 8 ++++++++ drivers/hv/Kconfig | 3 +++ 3 files changed, 18 insertions(+),

Hyper-V TSC page clocksource is suitable for vDSO, however, the protocol defined by the hypervisor is different from VCLOCK_PVCLOCK. Implement the required support re-using pvclock_page VVAR as VCLOCK_PVCLOCK is mutually exclusive with VCLOCK_HVCLOCK at run time. Signed-off-by: Vitaly Kuznetsov <vkuznets at redhat.com> --- arch/x86/entry/vdso/vclock_gettime.c | 48