From: Thomas Gleixner <tglx@linutronix.de>
To: Andy Lutomirski <luto@kernel.org>,
Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
nathanl@linux.ibm.com, Arnd Bergmann <arnd@arndb.de>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Andrew Lutomirski <luto@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
"open list\:MIPS" <linux-mips@vger.kernel.org>,
X86 ML <x86@kernel.org>
Subject: Re: [RFC PATCH v4 10/11] lib: vdso: Allow arches to override the ns shift operation
Date: Thu, 16 Jan 2020 20:57:03 +0100 [thread overview]
Message-ID: <877e1rfa40.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <CALCETrWJcB9=MuSw5yx6arcb_np=E=awTyLRSi=r8BJySf_aXw@mail.gmail.com>
Andy Lutomirski <luto@kernel.org> writes:
> On Thu, Jan 16, 2020 at 9:58 AM Christophe Leroy
>
> Would mul_u64_u64_shr() be a good alternative? Could we adjust it to
> assume the shift is less than 32? That function exists to benefit
> 32-bit arches.
We'd want mul_u64_u32_shr() for this. The rules for mult and shift are:
1 <= mult <= U32_MAX
1 <= shift <= 32
If we want to enforce a shift < 32 we need to limit that conditionally
in the calculation/registration function.
Thanks,
tglx
WARNING: multiple messages have this Message-ID (diff)
From: Thomas Gleixner <tglx@linutronix.de>
To: Andy Lutomirski <luto@kernel.org>,
Christophe Leroy <christophe.leroy@c-s.fr>
Cc: nathanl@linux.ibm.com, Arnd Bergmann <arnd@arndb.de>,
X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
"open list:MIPS" <linux-mips@vger.kernel.org>,
Paul Mackerras <paulus@samba.org>,
Andrew Lutomirski <luto@kernel.org>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [RFC PATCH v4 10/11] lib: vdso: Allow arches to override the ns shift operation
Date: Thu, 16 Jan 2020 20:57:03 +0100 [thread overview]
Message-ID: <877e1rfa40.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <CALCETrWJcB9=MuSw5yx6arcb_np=E=awTyLRSi=r8BJySf_aXw@mail.gmail.com>
Andy Lutomirski <luto@kernel.org> writes:
> On Thu, Jan 16, 2020 at 9:58 AM Christophe Leroy
>
> Would mul_u64_u64_shr() be a good alternative? Could we adjust it to
> assume the shift is less than 32? That function exists to benefit
> 32-bit arches.
We'd want mul_u64_u32_shr() for this. The rules for mult and shift are:
1 <= mult <= U32_MAX
1 <= shift <= 32
If we want to enforce a shift < 32 we need to limit that conditionally
in the calculation/registration function.
Thanks,
tglx
WARNING: multiple messages have this Message-ID (diff)
From: Thomas Gleixner <tglx@linutronix.de>
To: Andy Lutomirski <luto@kernel.org>,
Christophe Leroy <christophe.leroy@c-s.fr>
Cc: nathanl@linux.ibm.com, Arnd Bergmann <arnd@arndb.de>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
"open list:MIPS" <linux-mips@vger.kernel.org>,
Paul Mackerras <paulus@samba.org>,
Andrew Lutomirski <luto@kernel.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [RFC PATCH v4 10/11] lib: vdso: Allow arches to override the ns shift operation
Date: Thu, 16 Jan 2020 20:57:03 +0100 [thread overview]
Message-ID: <877e1rfa40.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <CALCETrWJcB9=MuSw5yx6arcb_np=E=awTyLRSi=r8BJySf_aXw@mail.gmail.com>
Andy Lutomirski <luto@kernel.org> writes:
> On Thu, Jan 16, 2020 at 9:58 AM Christophe Leroy
>
> Would mul_u64_u64_shr() be a good alternative? Could we adjust it to
> assume the shift is less than 32? That function exists to benefit
> 32-bit arches.
We'd want mul_u64_u32_shr() for this. The rules for mult and shift are:
1 <= mult <= U32_MAX
1 <= shift <= 32
If we want to enforce a shift < 32 we need to limit that conditionally
in the calculation/registration function.
Thanks,
tglx
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-01-16 19:57 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 17:58 [RFC PATCH v4 00/11] powerpc: switch VDSO to C implementation Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 01/11] powerpc/64: Don't provide time functions in compat VDSO32 Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 02/11] powerpc/vdso: Switch VDSO to generic C implementation Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 03/11] lib: vdso: only read hrtimer_res when needed in __cvdso_clock_getres() Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 04/11] powerpc/vdso: simplify __get_datapage() Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 05/11] lib: vdso: allow arches to provide vdso data pointer Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 06/11] powerpc/vdso: provide inline alternative to __get_datapage() Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 07/11] powerpc/vdso: provide vdso data pointer from the ASM caller Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 08/11] lib: vdso: allow fixed clock mode Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 20:13 ` Thomas Gleixner
2020-01-16 20:13 ` Thomas Gleixner
2020-01-16 20:13 ` Thomas Gleixner
2020-01-16 20:19 ` Andy Lutomirski
2020-01-16 20:19 ` Andy Lutomirski
2020-01-16 20:19 ` Andy Lutomirski
2020-01-16 21:07 ` Thomas Gleixner
2020-01-16 21:07 ` Thomas Gleixner
2020-01-16 21:07 ` Thomas Gleixner
2020-01-16 17:58 ` [RFC PATCH v4 09/11] powerpc/vdso: override __arch_vdso_capable() Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 10/11] lib: vdso: Allow arches to override the ns shift operation Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 19:47 ` Andy Lutomirski
2020-01-16 19:47 ` Andy Lutomirski
2020-01-16 19:47 ` Andy Lutomirski
2020-01-16 19:57 ` Thomas Gleixner [this message]
2020-01-16 19:57 ` Thomas Gleixner
2020-01-16 19:57 ` Thomas Gleixner
2020-01-16 20:20 ` Andy Lutomirski
2020-01-16 20:20 ` Andy Lutomirski
2020-01-16 20:20 ` Andy Lutomirski
2020-01-29 7:14 ` Thomas Gleixner
2020-01-29 7:14 ` Thomas Gleixner
2020-01-29 7:14 ` Thomas Gleixner
2020-01-29 7:26 ` Christophe Leroy
2020-01-29 7:26 ` Christophe Leroy
2020-01-29 7:26 ` Christophe Leroy
2020-01-16 17:58 ` [RFC PATCH v4 11/11] powerpc/32: provide vdso_shift_ns() Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-16 17:58 ` Christophe Leroy
2020-01-17 8:58 ` [RFC PATCH v4 00/11] powerpc: switch VDSO to C implementation Segher Boessenkool
2020-01-17 8:58 ` Segher Boessenkool
2020-01-17 8:58 ` Segher Boessenkool
2020-01-17 9:26 ` Christophe Leroy
2020-01-17 9:26 ` Christophe Leroy
2020-01-17 9:26 ` Christophe Leroy
2020-01-20 14:56 ` Christophe Leroy
2020-01-20 14:56 ` Christophe Leroy
2020-01-20 14:56 ` Christophe Leroy
2020-01-20 15:19 ` Segher Boessenkool
2020-01-20 15:19 ` Segher Boessenkool
2020-01-20 15:19 ` Segher Boessenkool
2020-01-20 17:08 ` Christophe Leroy
2020-01-20 17:08 ` Christophe Leroy
2020-01-20 17:08 ` Christophe Leroy
2020-01-20 17:27 ` Segher Boessenkool
2020-01-20 17:27 ` Segher Boessenkool
2020-01-20 17:27 ` Segher Boessenkool
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