RE: [PATCH v6 3/3] power: amd power monitor support

["Tummala, Sivaprasad" <Sivaprasad.Tummala@amd.com>]

[AMD Official Use Only - General]

Hi David,

> -----Original Message-----
> From: David Marchand <david.marchand@redhat.com>
> Sent: Tuesday, October 10, 2023 2:30 PM
> To: Tummala, Sivaprasad <Sivaprasad.Tummala@amd.com>
> Cc: david.hunt@intel.com; konstantin.v.ananyev@yandex.ru;
> roretzla@linux.microsoft.com; anatoly.burakov@intel.com; thomas@monjalon.net;
> Yigit, Ferruh <Ferruh.Yigit@amd.com>; dev@dpdk.org
> Subject: Re: [PATCH v6 3/3] power: amd power monitor support
>
> Caution: This message originated from an External Source. Use proper caution
> when opening attachments, clicking links, or responding.
>
>
> Hello Siva,
>
> On Mon, Oct 9, 2023 at 4:06 PM Sivaprasad Tummala
> <sivaprasad.tummala@amd.com> wrote:
> >
> > mwaitx allows EPYC processors to enter a implementation dependent
> > power/performance optimized state (C1 state) for a specific period or
> > until a store to the monitored address range.
> >
> > Signed-off-by: Sivaprasad Tummala <sivaprasad.tummala@amd.com>
> > Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>
> > ---
>
> Please put some changelog to make life easier for reviewers (and me).
>
> I diffed with the previous version to check what had been changed and I see this:
>
>  static void amd_mwaitx(const uint64_t timeout) ...
> -                       "c"(2), /* enable timer */
> -                       "b"(timeout));
> +                       "c"(0)); /* no time-out */
> /
> I will take this series as is, but please confirm why this change was needed.
>
Thanks for applying the patch set. The change was needed to fix compilation issue for 32-bit DPDK.

>
> >  lib/eal/x86/rte_power_intrinsics.c | 108
> > ++++++++++++++++++++++-------
> >  1 file changed, 84 insertions(+), 24 deletions(-)
> >
> > diff --git a/lib/eal/x86/rte_power_intrinsics.c
> > b/lib/eal/x86/rte_power_intrinsics.c
> > index 664cde01e9..0d2953f570 100644
> > --- a/lib/eal/x86/rte_power_intrinsics.c
> > +++ b/lib/eal/x86/rte_power_intrinsics.c
> > @@ -17,6 +17,78 @@ static struct power_wait_status {
> >         volatile void *monitor_addr; /**< NULL if not currently
> > sleeping */  } __rte_cache_aligned wait_status[RTE_MAX_LCORE];
> >
> > +/**
> > + * This functions uses UMONITOR/UMWAIT instructions and will enter C0.2 state.
>
> Fixed while applying, function*
>
> > + * For more information about usage of these instructions, please
> > +refer to
> > + * Intel(R) 64 and IA-32 Architectures Software Developer's Manual.
> > + */
> > +static void intel_umonitor(volatile void *addr) { #if
> > +defined(RTE_TOOLCHAIN_MSVC) || defined(__WAITPKG__)
> > +       /* cast away "volatile" when using the intrinsic */
> > +       _umonitor((void *)(uintptr_t)addr); #else
> > +       /*
> > +        * we're using raw byte codes for compiler versions which
> > +        * don't support this instruction natively.
> > +        */
> > +       asm volatile(".byte 0xf3, 0x0f, 0xae, 0xf7;"
> > +                       :
> > +                       : "D"(addr));
> > +#endif
> > +}
> > +
> > +static void intel_umwait(const uint64_t timeout) {
> > +       const uint32_t tsc_l = (uint32_t)timeout;
> > +       const uint32_t tsc_h = (uint32_t)(timeout >> 32); #if
> > +defined(RTE_TOOLCHAIN_MSVC) || defined(__WAITPKG__)
> > +       _umwait(tsc_l, tsc_h);
> > +#else
> > +       asm volatile(".byte 0xf2, 0x0f, 0xae, 0xf7;"
> > +                       : /* ignore rflags */
> > +                       : "D"(0), /* enter C0.2 */
> > +                         "a"(tsc_l), "d"(tsc_h)); #endif }
> > +
> > +/**
> > + * This functions uses MONITORX/MWAITX instructions and will enter C1 state.
> > + * For more information about usage of these instructions, please
> > +refer to
> > + * AMD64 Architecture Programmer’s Manual.
> > + */
> > +static void amd_monitorx(volatile void *addr) { #if
> > +defined(__MWAITX__)
>
> This part probably breaks build with MSVC.
>
> I could not determine whether MSVC supports this intrinsic.
> I'll rely on Tyler to fix it later.
>
>
> Series applied.
>
> --
> David Marchand