From: Peter Zijlstra <peterz@infradead.org>
To: Len Brown <lenb@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>,
Andy Lutomirski <luto@kernel.org>,
"Chang S. Bae" <chang.seok.bae@intel.com>,
Borislav Petkov <bp@suse.de>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, X86 ML <x86@kernel.org>,
"Brown, Len" <len.brown@intel.com>,
"Liu, Jing2" <jing2.liu@intel.com>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"Chen, Tim C" <tim.c.chen@intel.com>
Subject: Re: [PATCH v5 28/28] x86/fpu/amx: Clear the AMX state when appropriate
Date: Thu, 27 May 2021 13:56:33 +0200 [thread overview]
Message-ID: <YK+I8YEEnhWjuVAd@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAJvTdKmOLb0pt2SDgAKfwjxtMzT=t=UoREoPRUmi=4MWzeJ+QA@mail.gmail.com>
On Mon, May 24, 2021 at 02:24:54PM -0400, Len Brown wrote:
> On Mon, May 24, 2021 at 1:39 PM Dave Hansen <dave.hansen@intel.com> wrote:
>
> > >> might be considered nasty.
>
> > > I'm not excited about burdening the generic idle path with a CPU
> > > feature specific check that would need to be checked on every idle
> > > entry.
> >
> > Me neither.
> >
> > But, the check itself should be cheap. A cpu_feature_enabled(AMX) check
> > will eliminate even the cost of a branch on systems without AMX. You
> > could probably even get fancy and also use a static branch that doesn't
> > get enabled until the first AMX user shows up.
>
> It isn't just the hardware run-time cost.
> It is the source code complexity.
> That code is 100% generic.
Why can't this live in intel_idle.c ? We had to pull out
CPUIDLE_FLAG_TLB_FLUSH because leave_mm() requires RCU, but afaict both
TILERELEASE and XRESTOR do not and could be added to intel_idle_tile(),
which can be used in XXX_cstates[] for the relevant chips instead of
intel_idle() for C6 and up.
intel_idle_tile(args)
{
bool has_tile = // something XINUSE
if (has_tile)
TILERELEASE
intel_idle(args...);
if (has_tile)
// something XRESTOR
}
Hmm?
next prev parent reply other threads:[~2021-05-27 11:56 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-23 19:32 [PATCH v5 00/28] x86: Support Intel Advanced Matrix Extensions Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 01/28] x86/fpu/xstate: Modify the initialization helper to handle both static and dynamic buffers Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 02/28] x86/fpu/xstate: Modify state copy helpers " Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 03/28] x86/fpu/xstate: Modify address finders " Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 04/28] x86/fpu/xstate: Modify the context restore helper " Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 05/28] x86/fpu/xstate: Add a new variable to indicate dynamic user states Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 06/28] x86/fpu/xstate: Add new variables to indicate dynamic xstate buffer size Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 07/28] x86/fpu/xstate: Calculate and remember dynamic xstate buffer sizes Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 08/28] x86/fpu/xstate: Convert the struct fpu 'state' field to a pointer Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 09/28] x86/fpu/xstate: Introduce helpers to manage the xstate buffer dynamically Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 10/28] x86/fpu/xstate: Define the scope of the initial xstate data Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 11/28] x86/fpu/xstate: Update the xstate save function to support dynamic states Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 12/28] x86/fpu/xstate: Update the xstate buffer address finder " Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 13/28] x86/fpu/xstate: Update the xstate context copy function " Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 14/28] x86/fpu/xstate: Prevent unauthorised use of dynamic user state Chang S. Bae
2021-06-16 16:17 ` Dave Hansen
2021-06-16 16:27 ` Dave Hansen
2021-06-16 18:12 ` Andy Lutomirski
2021-06-16 18:47 ` Bae, Chang Seok
2021-06-16 19:01 ` Dave Hansen
2021-06-16 19:23 ` Bae, Chang Seok
2021-06-16 19:28 ` Dave Hansen
2021-06-16 19:37 ` Bae, Chang Seok
2021-06-28 10:11 ` Liu, Jing2
2021-06-29 17:43 ` Bae, Chang Seok
2021-06-29 17:54 ` Dave Hansen
2021-06-29 18:35 ` Bae, Chang Seok
2021-06-29 18:50 ` Dave Hansen
2021-06-29 19:13 ` Bae, Chang Seok
2021-06-29 19:26 ` Dave Hansen
2021-05-23 19:32 ` [PATCH v5 15/28] x86/arch_prctl: Create ARCH_GET_XSTATE/ARCH_PUT_XSTATE Chang S. Bae
2021-05-24 23:10 ` Len Brown
2021-05-25 17:27 ` Borislav Petkov
2021-05-25 17:33 ` Dave Hansen
2021-05-26 0:38 ` Len Brown
2021-05-27 11:14 ` second, sync-alloc syscall Borislav Petkov
2021-05-27 13:59 ` Len Brown
2021-05-27 19:35 ` Andy Lutomirski
2021-05-25 15:46 ` [PATCH v5 15/28] x86/arch_prctl: Create ARCH_GET_XSTATE/ARCH_PUT_XSTATE Dave Hansen
2021-05-23 19:32 ` [PATCH v5 16/28] x86/fpu/xstate: Support ptracer-induced xstate buffer expansion Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 17/28] x86/fpu/xstate: Adjust the XSAVE feature table to address gaps in state component numbers Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 18/28] x86/fpu/xstate: Disable xstate support if an inconsistent state is detected Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 19/28] x86/cpufeatures/amx: Enumerate Advanced Matrix Extension (AMX) feature bits Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 20/28] x86/fpu/amx: Define AMX state components and have it used for boot-time checks Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 21/28] x86/fpu/amx: Initialize child's AMX state Chang S. Bae
2021-05-24 3:09 ` Andy Lutomirski
2021-05-24 17:37 ` Len Brown
2021-05-24 18:13 ` Andy Lutomirski
2021-05-24 18:21 ` Len Brown
2021-05-25 3:44 ` Andy Lutomirski
2021-05-23 19:32 ` [PATCH v5 22/28] x86/fpu/amx: Enable the AMX feature in 64-bit mode Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 23/28] selftest/x86/amx: Test cases for the AMX state management Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 24/28] x86/fpu/xstate: Use per-task xstate mask for saving xstate in signal frame Chang S. Bae
2021-05-24 3:15 ` Andy Lutomirski
2021-05-24 18:06 ` Len Brown
2021-05-25 4:47 ` Andy Lutomirski
2021-05-25 14:04 ` Len Brown
2021-05-23 19:32 ` [PATCH v5 25/28] x86/fpu/xstate: Skip writing zeros to signal frame for dynamic user states if in INIT-state Chang S. Bae
2021-05-24 3:25 ` Andy Lutomirski
2021-05-24 18:15 ` Len Brown
2021-05-24 18:29 ` Dave Hansen
2021-05-25 4:46 ` Andy Lutomirski
2021-05-23 19:32 ` [PATCH v5 26/28] selftest/x86/amx: Test case for AMX state copy optimization in signal delivery Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 27/28] x86/insn/amx: Add TILERELEASE instruction to the opcode map Chang S. Bae
2021-05-23 19:32 ` [PATCH v5 28/28] x86/fpu/amx: Clear the AMX state when appropriate Chang S. Bae
2021-05-24 3:13 ` Andy Lutomirski
2021-05-24 14:10 ` Dave Hansen
2021-05-24 17:32 ` Len Brown
2021-05-24 17:39 ` Dave Hansen
2021-05-24 18:24 ` Len Brown
2021-05-27 11:56 ` Peter Zijlstra [this message]
2021-05-27 14:02 ` Len Brown
2021-05-24 14:06 ` Dave Hansen
2021-05-24 17:34 ` Len Brown
2021-05-24 21:11 ` [PATCH v5-fix " Chang S. Bae
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