From: Andy Lutomirski <luto@kernel.org>
To: Andy Lutomirski <luto@kernel.org>
Cc: "Bae, Chang Seok" <chang.seok.bae@intel.com>,
Dave Hansen <dave.hansen@intel.com>, X86 ML <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
libc-alpha <libc-alpha@sourceware.org>,
Florian Weimer <fweimer@redhat.com>,
Rich Felker <dalias@libc.org>, Kyle Huey <me@kylehuey.com>,
Keno Fischer <keno@juliacomputing.com>,
Linux API <linux-api@vger.kernel.org>
Subject: Re: Candidate Linux ABI for Intel AMX and hypothetical new related features
Date: Fri, 26 Mar 2021 16:18:14 -0700 [thread overview]
Message-ID: <CALCETrUBC34NSHj3eLScYtHJk_7ZHOVJZVPkdLUXemPEiyA_uA@mail.gmail.com> (raw)
In-Reply-To: <CALCETrW2QHa2TLvnUuVxAAheqcbSZ-5_WRXtDSAGcbG8N+gtdQ@mail.gmail.com>
Sigh, cc linux-api, not linux-abi.
On Fri, Mar 26, 2021 at 4:12 PM Andy Lutomirski <luto@kernel.org> wrote:
>
> Hi all-
>
> After some discussion on IRC, I have a proposal for a Linux ABI for
> using Intel AMX and other similar features. It works like this:
>
> First, we make XCR0 dynamic. This looks a lot like Keno's patch but
> with a different API, outlined below. Different tasks can have
> different XCR0 values. The default XCR0 for new tasks does not
> include big features like AMX. XMM and YMM are still there. The AVX2
> states are debatable -- see below.
>
> To detect features and control XCR0, we add some new arch_prctls:
>
> arch_prctl(ARCH_GET_XCR0_SUPPORT, 0, ...);
>
> returns the set of XCR0 bits supported on the current kernel.
>
> arch_prctl(ARCH_GET_XCR0_LAZY_SUPPORT, 0, ...);
>
> returns 0. See below.
>
> arch_prctl(ARCH_SET_XCR0, xcr0, lazy_states, sigsave_states,
> sigclear_states, 0);
>
> Sets xcr0. All states are preallocated except that states in
> lazy_states may be unallocated in the kernel until used. (Not
> supported at all in v1. lazy_states & ~xcr0 != 0 is illegal.) States
> in sigsave_states are saved in the signal frame. States in
> sigclear_states are reset to the init state on signal delivery.
> States in sigsave_states are restored by sigreturn, and states not in
> sigsave_states are left alone by sigreturn.
>
> Optionally we do not support PKRU at all in XCR0 -- it doesn't make
> that much sense as an XSAVE feature, and I'm not convinced that trying
> to correctly context switch XINUSE[PKRU] is worthwhile. I doubt we
> get it right today.
>
> Optionally we come up with a new format for new features in the signal
> frame, since the current format is showing its age. Taking 8kB for a
> signal with AMX is one thing. Taking another 8kB for a nested signal
> if AMX is not in use is worse.
>
> Optionally we make AVX-512 also default off, which fixes what is
> arguably a serious ABI break with AVX-512: lots of programs, following
> POSIX (!), seem to think that they know much much space to allocate
> for sigaltstack(). AVX-512 is too big.
>
> Thoughts?
>
> --Andy
next parent reply other threads:[~2021-03-26 23:20 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CALCETrW2QHa2TLvnUuVxAAheqcbSZ-5_WRXtDSAGcbG8N+gtdQ@mail.gmail.com>
2021-03-26 23:18 ` Andy Lutomirski [this message]
2021-03-27 3:39 ` Candidate Linux ABI for Intel AMX and hypothetical new related features Len Brown
2021-03-27 9:14 ` Borislav Petkov
2021-03-27 9:58 ` Greg KH
2021-03-29 15:47 ` Len Brown
2021-03-29 16:38 ` Len Brown
2021-03-29 16:48 ` Florian Weimer
2021-03-29 18:14 ` Andy Lutomirski
2021-03-29 18:16 ` Andy Lutomirski
2021-03-29 22:38 ` Len Brown
2021-03-30 5:08 ` Andy Lutomirski
2021-03-30 5:50 ` Noah Goldstein
2021-03-30 17:01 ` Len Brown
2021-03-30 17:05 ` Andy Lutomirski
2021-03-30 17:56 ` Len Brown
2021-03-30 19:12 ` Dave Hansen
2021-03-30 20:20 ` Andy Lutomirski
2021-03-30 20:42 ` Len Brown
2021-03-30 22:01 ` David Laight
2021-03-31 16:31 ` Len Brown
2021-03-31 16:53 ` Andy Lutomirski
2021-03-31 21:42 ` Robert O'Callahan
2021-03-31 22:11 ` Len Brown
2021-03-31 22:28 ` Len Brown
2021-03-31 22:45 ` Andy Lutomirski
2021-04-09 20:52 ` Len Brown
2021-04-09 21:44 ` Andy Lutomirski
2021-04-11 19:07 ` Len Brown
2021-04-12 7:59 ` David Laight
2021-04-12 12:19 ` Borislav Petkov
2021-04-12 17:14 ` Sean Christopherson
2021-03-31 22:52 ` Borislav Petkov
2021-04-09 20:55 ` Len Brown
2021-03-28 0:53 ` Thomas Gleixner
2021-03-29 7:27 ` Peter Zijlstra
2021-03-29 15:06 ` Dave Hansen
[not found] <20210415044258.GA6318@zn.tnic>
[not found] ` <20210415052938.GA2325@1wt.eu>
[not found] ` <20210415054713.GB6318@zn.tnic>
[not found] ` <CAJvTdKnjzAMh3N_c7KP3kA=e0LgYHgCANg44oJp3LcSm7dtbSQ@mail.gmail.com>
[not found] ` <20210419141454.GE9093@zn.tnic>
[not found] ` <CAJvTdK=p8mgO3xw9sRxu0c7NTNTG109M442b3UZh8TqLLfkC1Q@mail.gmail.com>
[not found] ` <20210419191539.GH9093@zn.tnic>
[not found] ` <CAJvTdK=VnG94ECcRVoUi8HrCbVEKc8X4_JmRTkqe+vTttf0Wsg@mail.gmail.com>
[not found] ` <20210419215809.GJ9093@zn.tnic>
[not found] ` <CAJvTdKn6JHo02karEs0e5g+6SimS5VUcXKjCkX35WY+xkgAgxw@mail.gmail.com>
[not found] ` <YIMmwhEr46VPAZa4@zn.tnic>
[not found] ` <CAJvTdKnhXnynybS4eNEF_EtF26auyb-mhKLNd1D9_zvCrchZsw@mail.gmail.com>
2021-05-17 9:45 ` Thomas Gleixner
2021-05-17 9:56 ` Florian Weimer
2021-05-17 10:18 ` Thomas Gleixner
2021-05-21 16:29 ` Len Brown
2021-05-17 13:49 ` Arjan van de Ven
2021-05-20 15:35 ` Len Brown
2021-05-20 20:54 ` Thomas Gleixner
2021-05-20 21:13 ` Dave Hansen
2021-05-20 21:41 ` Len Brown
2021-05-20 22:53 ` Dave Hansen
2021-05-21 9:41 ` Thomas Gleixner
2021-05-21 14:44 ` Florian Weimer
2021-05-21 14:49 ` Peter Zijlstra
2021-06-23 15:06 ` Florian Weimer
2021-06-23 23:11 ` Len Brown
2021-06-28 10:14 ` Enrico Weigelt, metux IT consult
2021-06-28 12:49 ` Florian Weimer
2021-06-30 12:22 ` Enrico Weigelt, metux IT consult
2021-06-30 12:41 ` Willy Tarreau
2021-06-30 13:55 ` Arjan van de Ven
2021-06-30 15:20 ` Len Brown
2021-06-30 15:25 ` Enrico Weigelt, metux IT consult
2021-05-21 16:14 ` Dave Hansen
2021-05-21 16:19 ` Florian Weimer
2021-05-21 16:26 ` Len Brown
2021-05-21 16:28 ` Dave Hansen
2021-05-21 16:31 ` Andy Lutomirski
2021-05-21 19:10 ` Thomas Gleixner
2021-05-21 20:07 ` Andy Lutomirski
2021-05-21 21:43 ` Thomas Gleixner
2021-05-21 22:07 ` Len Brown
2021-05-21 22:46 ` Thomas Gleixner
2021-05-21 23:31 ` Len Brown
2021-05-22 7:16 ` Florian Weimer
2021-05-22 23:55 ` Andy Lutomirski
2021-05-21 23:06 ` Dave Hansen
2021-05-21 23:08 ` Len Brown
2021-05-21 19:05 ` Thomas Gleixner
2021-05-20 21:22 ` Len Brown
2021-05-20 21:41 ` Thomas Gleixner
2021-05-20 21:49 ` Len Brown
2021-05-21 9:26 ` Thomas Gleixner
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