From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Thomas Gleixner <tglx@linutronix.de>, luto@kernel.org
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
arnd@arndb.de, vincenzo.frascino@arm.com, x86@kernel.org,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org
Subject: Re: [RFC PATCH v3 08/12] lib: vdso: allow arches to provide vdso data pointer
Date: Thu, 16 Jan 2020 10:16:18 +0100 [thread overview]
Message-ID: <b5fddcf8-99ff-fc0d-40c0-0eb81ad4e94a@c-s.fr> (raw)
In-Reply-To: <d2de3211-9d7c-513e-fe0f-8bdce623fb65@c-s.fr>
Thomas, Andy,
Le 15/01/2020 à 07:15, Christophe Leroy a écrit :
>
>
> Le 15/01/2020 à 00:06, Thomas Gleixner a écrit :
>> Christophe Leroy <christophe.leroy@c-s.fr> writes:
>>> static __maybe_unused int
>>> +#ifdef VDSO_GETS_VD_PTR_FROM_ARCH
>>> +__cvdso_clock_gettime_common(const struct vdso_data *vd, clockid_t
>>> clock,
>>> + struct __kernel_timespec *ts)
>>> +{
>>> +#else
>>> __cvdso_clock_gettime_common(clockid_t clock, struct
>>> __kernel_timespec *ts)
>>> {
>>> const struct vdso_data *vd = __arch_get_vdso_data();
>>> +#endif
>>> u32 msk;
>>
>> If we do that, then there is no point in propagating this to the inner
>> functions. It's perfectly fine to have this distinction at the outermost
>> level.
>
> In v2, I did it at the arch level (see
> https://patchwork.ozlabs.org/patch/1214983/). Andy was concerned about
> it being suboptimal for arches which (unlike powerpc) have PC related
> data addressing mode.
>
> Wouldn't it be the same issue if doing it at the outermost level of
> generic VDSO ?
Any opinion on this ?
From your point of view, what should I do:
A/ __arch_get_vdso_data() handled entirely at arch level and arches
handing over the vdso data pointer to generic C VDSO functions all the
time (as in my v2 series) ?
B/ Data pointer being handed over all the way up for arches wanting to
do so, no changes at all for others (as in my v3 series) ?
C/ __arch_get_vdso_data() being called at the outermost generic level
for arches not interested in handling data pointer from the caller (as
suggested by Thomas) ?
Andy, with A/ you were concerned about arches being able to do PC
related accesses. Would it be an issue for C/ as well ? If not, I guess
C/ would be cleaner than B/ allthought not as clean as A which doesn't
add any #ifdefery at all.
Thanks
Christophe
next prev parent reply other threads:[~2020-01-16 9:16 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-13 17:08 [RFC PATCH v3 00/12] powerpc: switch VDSO to C implementation Christophe Leroy
2020-01-13 17:08 ` [RFC PATCH v3 01/12] powerpc/64: Don't provide time functions in compat VDSO32 Christophe Leroy
2020-01-13 17:08 ` [RFC PATCH v3 02/12] powerpc/vdso: Switch VDSO to generic C implementation Christophe Leroy
2020-01-13 17:08 ` [RFC PATCH v3 03/12] lib: vdso: mark __cvdso_clock_getres() as static Christophe Leroy
2020-01-13 17:08 ` [RFC PATCH v3 04/12] lib: vdso: inline do_hres() and do_coarse() Christophe Leroy
2020-01-13 17:08 ` [RFC PATCH v3 05/12] lib: vdso: Avoid duplication in __cvdso_clock_getres() Christophe Leroy
2020-01-13 17:08 ` [RFC PATCH v3 06/12] lib: vdso: __iter_div_u64_rem() is suboptimal for 32 bit time Christophe Leroy
2020-01-14 11:31 ` Thomas Gleixner
2020-01-13 17:08 ` [RFC PATCH v3 07/12] powerpc/vdso: simplify __get_datapage() Christophe Leroy
2020-01-13 17:08 ` [RFC PATCH v3 08/12] lib: vdso: allow arches to provide vdso data pointer Christophe Leroy
2020-01-14 23:06 ` Thomas Gleixner
2020-01-15 6:15 ` Christophe Leroy
2020-01-16 9:16 ` Christophe Leroy [this message]
2020-01-16 10:35 ` Thomas Gleixner
2020-01-16 20:22 ` Andy Lutomirski
2020-01-13 17:08 ` [RFC PATCH v3 09/12] powerpc/vdso: provide inline alternative to __get_datapage() Christophe Leroy
2020-01-13 17:08 ` [RFC PATCH v3 10/12] powerpc/vdso: provide vdso data pointer from the ASM caller Christophe Leroy
2020-01-13 17:08 ` [RFC PATCH v3 11/12] lib: vdso: split clock verification out of __arch_get_hw_counter() Christophe Leroy
2020-01-13 17:08 ` [RFC PATCH v3 12/12] powerpc/vdso: provide __arch_is_hw_counter_valid() Christophe Leroy
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