From: "H. Peter Anvin" <hpa@zytor.com>
To: Stefani Seibold <stefani@seibold.net>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de,
mingo@redhat.com, ak@linux.intel.com, aarcange@redhat.com,
john.stultz@linaro.org, luto@amacapital.net
Subject: Re: [PATCH] Add VDSO time function support for x86 32-bit kernel
Date: Wed, 12 Dec 2012 22:14:25 -0800 [thread overview]
Message-ID: <1d3061cb-76d0-4e42-9b75-a975b05384ec@email.android.com> (raw)
In-Reply-To: <1355378005.24283.11.camel@wall-e>
This is too late for 3.8 anyway, so there is time to make it work correctly before tge 3.9 merge window anyway. After this merge window is over I may pull tjis into a testing branch, but compat support is a precondition.
The vdso is only optional if you build in backwards compatibility anyway, and software has a right to expect a specific numeric kernel version to export a single ABI.
Stefani Seibold <stefani@seibold.net> wrote:
>Am Mittwoch, den 12.12.2012, 15:34 -0800 schrieb H. Peter Anvin:
>> On 12/12/2012 12:19 PM, stefani@seibold.net wrote:
>> > diff --git a/arch/x86/vdso/vdso32/vclock_gettime.c
>b/arch/x86/vdso/vdso32/vclock_gettime.c
>> > new file mode 100644
>> > index 0000000..c9a1909
>> > --- /dev/null
>> > +++ b/arch/x86/vdso/vdso32/vclock_gettime.c
>> > @@ -0,0 +1,7 @@
>> > +/*
>> > + * since vgtod layout differs between X86_64 and x86_32, it is not
>possible to
>> > + * provide a 32 bit vclock with a 64 bit kernel
>> > + */
>> > +#ifdef CONFIG_X86_32
>> > +#include "../vclock_gettime.c"
>> > +#endif
>>
>> This is where this goes fail. Sorry, it is not acceptable to
>introduce
>> an ABI on x86-32 without providing it also on x86-64 in compatibility
>mode.
>>
>> I also don't believe it is not possible... it might require some more
>
>> cleverness; perhaps we need to do the 32-bit vgtod in such a way that
>it
>> *is* compatible with 64 bits.
>>
>
>The comment is ambiguous:
>
>Since vgtod layout differs between X86_64 and x86_32 AND the vgtod is
>not inside the accessible address space of a 32 bit program, it is
>CURRENTLY not possible to provide a 32 bit vclock with a 64 bit kernel
>
>As i understand VDSO it is an alternativ way, so if there is no support
>for it, there must be a fall back to the system call interface in the
>program or lib, which tries to use it.
>
>So there is no drawback for 32 bit programs running on a 64 bit kernel.
>
>
>I think this feature is not so important and can implemented in a
>subsequent patch, because a 64 bit kernel system mostly runs 64 bit
>programs. Let us fix this things step by step.
>
>- Stefani
--
Sent from my mobile phone. Please excuse brevity and lack of formatting.
next prev parent reply other threads:[~2012-12-13 6:14 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-12 20:19 [PATCH] Add VDSO time function support for x86 32-bit kernel stefani
2012-12-12 23:34 ` H. Peter Anvin
2012-12-13 5:53 ` Stefani Seibold
2012-12-13 6:10 ` H. Peter Anvin
2012-12-13 6:14 ` H. Peter Anvin [this message]
2012-12-13 6:17 ` Stefani Seibold
2012-12-13 6:47 ` H. Peter Anvin
2012-12-13 7:17 ` Stefani Seibold
2012-12-13 19:32 ` Andy Lutomirski
2012-12-14 0:09 ` H. Peter Anvin
2012-12-14 0:20 ` Andy Lutomirski
2012-12-14 0:36 ` H. Peter Anvin
2012-12-14 1:32 ` H. Peter Anvin
2012-12-14 1:42 ` Andy Lutomirski
2012-12-14 1:49 ` H. Peter Anvin
2012-12-14 2:11 ` Andy Lutomirski
2012-12-14 2:18 ` H. Peter Anvin
2012-12-14 2:20 ` Andy Lutomirski
2012-12-14 8:34 ` [CRIU] " Pavel Emelyanov
2012-12-14 18:35 ` H. Peter Anvin
2012-12-14 18:44 ` Andy Lutomirski
2012-12-14 18:47 ` H. Peter Anvin
2012-12-14 20:12 ` Cyrill Gorcunov
2012-12-14 21:08 ` H. Peter Anvin
2012-12-14 21:20 ` Cyrill Gorcunov
2012-12-14 21:21 ` H. Peter Anvin
2012-12-14 21:27 ` Andy Lutomirski
2012-12-14 22:00 ` H. Peter Anvin
2012-12-14 22:25 ` Cyrill Gorcunov
2012-12-14 22:27 ` H. Peter Anvin
2012-12-14 22:43 ` Cyrill Gorcunov
2012-12-14 22:48 ` H. Peter Anvin
2012-12-14 23:48 ` John Stultz
2012-12-14 23:55 ` H. Peter Anvin
2012-12-17 9:05 ` Pavel Emelyanov
[not found] ` <fb2e871b-3e2a-4e96-9eb9-cb2dd4f66eaa@email.android! .com>
2012-12-17 15:21 ` H. Peter Anvin
2012-12-17 18:56 ` Pavel Emelyanov
2012-12-17 18:57 ` H. Peter Anvin
2012-12-14 22:46 ` H. Peter Anvin
2012-12-14 23:09 ` Stefani Seibold
2012-12-14 23:29 ` H. Peter Anvin
-- strict thread matches above, loose matches on Subject: below --
2012-12-11 16:11 stefani
2012-12-11 19:27 ` John Stultz
2012-12-11 19:37 ` Andy Lutomirski
2012-12-11 20:54 ` Stefani Seibold
2012-12-11 21:18 ` Andy Lutomirski
2012-12-11 21:28 ` Stefani Seibold
2012-12-11 19:37 ` Andy Lutomirski
2012-12-11 20:40 ` Stefani Seibold
2012-12-12 1:29 ` Andy Lutomirski
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