* Peter Zijlstra:
On Fri, May 21, 2021 at 04:44:58PM +0200, Florian Weimer wrote:
quoted
And we added an interface for querying x86 CPU features to glibc 2.33
which is completely incompatible with this because it assumes that CPU
features do not change during the lifetime of a process. 8-(
How many x86 kernel maintainers signed off on that patch?
I've started a new thread:
x86 CPU features detection for applications (and AMX)
<https://lore.kernel.org/linux-api/87tulo39ms.fsf@oldenburg.str.redhat.com/>
Thanks,
Florian
On Wed, Jun 23, 2021 at 11:07 AM Florian Weimer [off-list ref] wrote:
* Peter Zijlstra:
quoted
On Fri, May 21, 2021 at 04:44:58PM +0200, Florian Weimer wrote:
quoted
And we added an interface for querying x86 CPU features to glibc 2.33
which is completely incompatible with this because it assumes that CPU
features do not change during the lifetime of a process. 8-(
How many x86 kernel maintainers signed off on that patch?
I've started a new thread:
x86 CPU features detection for applications (and AMX)
<https://lore.kernel.org/linux-api/87tulo39ms.fsf@oldenburg.str.redhat.com/>
FWIW, I didn't receive it, because you excluded
linux-kernel@vger.kernel.org
(x86@kernel.org is just the actual x86 kernel committers, ISTR)
Len Brown, Intel Open Source Technology Center
On 24.06.21 01:11, Len Brown wrote:
quoted
x86 CPU features detection for applications (and AMX)
<https://lore.kernel.org/linux-api/87tulo39ms.fsf@oldenburg.str.redhat.com/>
FWIW, I didn't receive it, because you excluded
linux-kernel@vger.kernel.org
me neither :(
Maybe just repost it to LKML ?
You mention the interface *was* designed with cpu features remaining
constant over a process' lifetime. Between the line I'm reading that
this might not be the case anymore.
How could that happen ? Process migration on a different CPU (or perhaps
on a different host) ?
This is gonna be tricky, because this somehow needs to be synchronized
with the application (even if we check the bits before calling some
cpu-specific opcode, which also has some performance cost), there's
still some window where the application might not yet recognize the
change. So either we need some explicit migration points (where app
tells, please let me finish this func first) or transparent emulation.
Damn, how could the cpu designers come up with such weird concepts
in the first place ? :o
--mtx
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Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
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