From: "Thomas Weißschuh" <thomas.weissschuh@linutronix.de>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Madhavan Srinivasan <maddy@linux.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Nicholas Piggin <npiggin@gmail.com>,
Christophe Leroy <chleroy@kernel.org>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, linux-mips@vger.kernel.org
Subject: Re: [PATCH 5/7] MIPS: VDSO: Drop kconfig MIPS_CLOCK_VSYSCALL
Date: Fri, 27 Feb 2026 10:31:58 +0100 [thread overview]
Message-ID: <20260227100849-fb0bfec5-4d67-409c-8dc4-dad10c84fe98@linutronix.de> (raw)
In-Reply-To: <7fb5b531-2d78-409f-8f65-e12757f9296e@app.fastmail.com>
On Fri, Feb 27, 2026 at 09:46:23AM +0100, Arnd Bergmann wrote:
> On Fri, Feb 27, 2026, at 07:57, Thomas Weißschuh wrote:
> > This configuration option exists so "that we don't provide the symbol
> > when there's no possibility of there being a usable clocksource".
> > However it only covers __vdso_gettimeofday() and none of the other vDSO
> > functions which should be affected by the same circumstances.
> > As these are more widely used than gettimeofday() and nobody seems to
> > have had an issue with them so far, drop MIPS_CLOCK_VSYSCALL completely.
> >
> > The removal of the ifdeffery will also make some upcomming changes
> > easier to read.
> >
> > Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
>
> The #ifdef was originally been added in commit 7d2aa4bb90f5 ("mips:
> Fix gettimeofday() in the vdso library") as a bug fix. This may not
> have been the correct fix because I don't see how it addressed the
> case of a kernel with MIPS_CLOCK_VSYSCALL enabled running on a
> CPU without the timer registers, but I think we should try to make
> sure that there is no regression from reverting it now.
I can't make sense out of this commit. The generic vDSO automatically falls
back to the syscall if it can not handle the current clocksource.
There is no explanation *why* this should be broken on MIPS.
It works correctly on my x86 machines.
I will try to reproduce this in QEMU by removing the vDSO capability from
the respective clocksources.
Also vdso_clock_gettime() uses the same codepaths as vdso_gettimeofday()
and apparently that is not broken.
> > -config MIPS_CLOCK_VSYSCALL
> > - def_bool CSRC_R4K || CLKSRC_MIPS_GIC
> > -
>
> An easy alternative might be to drop the entire VDSO in
> configurations that turn off the gettimeofday vsyscall today:
>
> diff --git a/arch/mips/vdso/Kconfig b/arch/mips/vdso/Kconfig
> index 70140248da72..4f6fba9e108f 100644
> --- a/arch/mips/vdso/Kconfig
> +++ b/arch/mips/vdso/Kconfig
> @@ -3,4 +3,4 @@
> # the lack of relocations. As such, we disable the VDSO for microMIPS builds.
>
> config MIPS_DISABLE_VDSO
> - def_bool CPU_MICROMIPS
> + def_bool CPU_MICROMIPS || !(CSRC_R4K || CLKSRC_MIPS_GIC)
That is an an independent optimization IMO.
Thomas
next prev parent reply other threads:[~2026-02-27 9:32 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-27 6:57 [PATCH 0/7] vDSO: Respect COMPAT_32BIT_TIME Thomas Weißschuh
2026-02-27 6:57 ` [PATCH 1/7] x86/vdso: " Thomas Weißschuh
2026-02-27 8:51 ` Arnd Bergmann
2026-02-27 8:58 ` Arnd Bergmann
2026-02-27 9:34 ` Thomas Weißschuh
2026-03-03 18:11 ` H. Peter Anvin
2026-03-03 20:50 ` Arnd Bergmann
2026-03-03 21:00 ` H. Peter Anvin
2026-03-03 21:27 ` Arnd Bergmann
2026-03-03 21:36 ` H. Peter Anvin
2026-04-10 7:24 ` Thomas Weißschuh
2026-04-13 15:59 ` Arnd Bergmann
2026-04-13 16:13 ` Thomas Weißschuh
2026-04-13 16:57 ` Arnd Bergmann
2026-04-14 10:16 ` Thomas Weißschuh
2026-03-04 7:35 ` Thomas Weißschuh
2026-03-04 18:30 ` H. Peter Anvin
2026-03-05 9:24 ` Thomas Weißschuh
2026-03-05 23:57 ` H. Peter Anvin
2026-03-06 9:42 ` Thomas Weißschuh
2026-03-06 20:52 ` H. Peter Anvin
2026-02-27 6:57 ` [PATCH 2/7] ARM: VDSO: " Thomas Weißschuh
2026-02-27 6:57 ` [PATCH 3/7] arm64: vdso32: " Thomas Weißschuh
2026-02-27 6:57 ` [PATCH 4/7] powerpc/vdso: " Thomas Weißschuh
2026-02-27 6:57 ` [PATCH 5/7] MIPS: VDSO: Drop kconfig MIPS_CLOCK_VSYSCALL Thomas Weißschuh
2026-02-27 8:46 ` Arnd Bergmann
2026-02-27 9:31 ` Thomas Weißschuh [this message]
2026-02-27 10:03 ` Arnd Bergmann
2026-02-27 10:17 ` Thomas Weißschuh
2026-02-27 6:57 ` [PATCH 6/7] MIPS: VDSO: Respect COMPAT_32BIT_TIME Thomas Weißschuh
2026-02-27 6:57 ` [PATCH 7/7] vdso/gettimeofday: Verify COMPAT_32BIT_TIME interactions Thomas Weißschuh
2026-02-27 8:49 ` Arnd Bergmann
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