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From: "Bae, Chang Seok" <chang.seok.bae@intel.com>
To: "Lutomirski, Andy" <luto@amacapital.net>,
	"Hansen, Dave" <dave.hansen@intel.com>
Cc: "mingo@kernel.org" <mingo@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"bp@suse.de" <bp@suse.de>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"Liu, Jing2" <jing2.liu@intel.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"luto@kernel.org" <luto@kernel.org>,
	"Shankar, Ravi V" <ravi.v.shankar@intel.com>,
	"Brown, Len" <len.brown@intel.com>
Subject: Re: [RFC PATCH 13/22] x86/fpu/xstate: Expand dynamic user state area on first use
Date: Tue, 3 Nov 2020 21:53:22 +0000	[thread overview]
Message-ID: <978ba3b768214048b26619e0003db50c9d9c0792.camel@intel.com> (raw)
In-Reply-To: <be49f086-4135-7859-d88a-8c0444d20087@intel.com>

On Tue, 2020-11-03 at 13:41 -0800, Dave Hansen wrote:
> On 11/3/20 1:32 PM, Bae, Chang Seok wrote:
> > On Wed, 2020-10-14 at 09:29 -0700, Dave Hansen wrote:
> > > On 10/14/20 9:10 AM, Andy Lutomirski wrote:
> > > > I was suggesting something a little bit different.  We'd keep XMM,
> > > > YMM, ZMM, etc state stored exactly the way we do now and, for
> > > > AMX-using tasks, we would save the AMX state in an entirely
> > > > separate
> > > > buffer.  This way the pain of having a variable xstate layout is
> > > > confined just to AMX tasks.
> > > 
> > > OK, got it.
> > > 
> > > So, we'd either need a second set of XSAVE/XRSTORs, or "manual"
> > > copying
> > > of the registers out to memory.  We can preserve the modified
> > > optimization if we're careful about ordering, but only for *ONE* of
> > > the
> > > XSAVE buffers (if we use two).
> > 
> > For what is worth,
> > 
> > If using two buffers, the buffer for saving the tile data also needs
> > space
> > for the legacy states.
> 
> Just to be clear, you're talking about the 512-byte 'struct
> fxregs_state' which is the first member of 'struct xregs_state', right?

Yes.

> 
> > The AMX state is stored at the end of the XSAVE buffer (at least for
> > now).
> > So, the layout (in terms of offsets of non-AMX states) won't be changed
> > at
> > run-time.
> 
> I don't know what point you are trying to make here.

I was trying to clarify the concern that Andy had:

	"the pain of having a variable xstate layout"

Thanks,
Chang

  reply	other threads:[~2020-11-03 21:53 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-01 20:38 [RFC PATCH 00/22] x86: Support Intel Advanced Matrix Extensions Chang S. Bae
2020-10-01 20:38 ` [RFC PATCH 01/22] x86/fpu/xstate: Modify area init helper prototypes to access all the possible areas Chang S. Bae
2020-10-01 20:38 ` [RFC PATCH 02/22] x86/fpu/xstate: Modify xstate copy " Chang S. Bae
2020-10-01 20:38 ` [RFC PATCH 03/22] x86/fpu/xstate: Modify address finder " Chang S. Bae
2020-10-01 20:38 ` [RFC PATCH 04/22] x86/fpu/xstate: Modify save and restore helper " Chang S. Bae
2020-10-01 20:38 ` [RFC PATCH 05/22] x86/fpu/xstate: Introduce a new variable for dynamic user states Chang S. Bae
2020-10-01 20:38 ` [RFC PATCH 06/22] x86/fpu/xstate: Outline dynamic xstate area size in the task context Chang S. Bae
2020-10-01 20:38 ` [RFC PATCH 07/22] x86/fpu/xstate: Introduce helpers to manage an xstate area dynamically Chang S. Bae
2020-10-01 23:41   ` Andy Lutomirski
2020-10-13 22:00     ` Brown, Len
2020-10-01 20:38 ` [RFC PATCH 08/22] x86/fpu/xstate: Define the scope of the initial xstate data Chang S. Bae
2020-10-01 20:39 ` [RFC PATCH 09/22] x86/fpu/xstate: Introduce wrapper functions for organizing xstate area access Chang S. Bae
2020-10-01 20:39 ` [RFC PATCH 10/22] x86/fpu/xstate: Update xstate save function for supporting dynamic user xstate Chang S. Bae
2020-10-01 20:39 ` [RFC PATCH 11/22] x86/fpu/xstate: Update xstate area address finder " Chang S. Bae
2020-10-01 20:39 ` [RFC PATCH 12/22] x86/fpu/xstate: Update xstate context copy function for supporting dynamic area Chang S. Bae
2020-10-01 20:39 ` [RFC PATCH 13/22] x86/fpu/xstate: Expand dynamic user state area on first use Chang S. Bae
2020-10-01 23:39   ` Andy Lutomirski
2020-10-13 22:31     ` Brown, Len
2020-10-13 22:43       ` Dave Hansen
2020-10-14  1:11         ` Andy Lutomirski
2020-10-14  6:03           ` Dave Hansen
2020-10-14 16:10             ` Andy Lutomirski
2020-10-14 16:29               ` Dave Hansen
2020-11-03 21:32                 ` Bae, Chang Seok
2020-11-03 21:41                   ` Dave Hansen
2020-11-03 21:53                     ` Bae, Chang Seok [this message]
2020-10-14 10:41         ` Peter Zijlstra
2020-10-14  1:47       ` Andy Lutomirski
2020-10-01 20:39 ` [RFC PATCH 14/22] x86/fpu/xstate: Inherit dynamic user state when used in the parent Chang S. Bae
2020-10-01 20:39 ` [RFC PATCH 15/22] x86/fpu/xstate: Support ptracer-induced xstate area expansion Chang S. Bae
2020-10-01 20:39 ` [RFC PATCH 16/22] x86/fpu/xstate: Support dynamic user state in the signal handling path Chang S. Bae
2020-10-01 20:39 ` [RFC PATCH 17/22] x86/fpu/xstate: Extend the table for mapping xstate components with features Chang S. Bae
2020-10-01 20:39 ` [RFC PATCH 18/22] x86/cpufeatures/amx: Enumerate Advanced Matrix Extension (AMX) feature bits Chang S. Bae
2020-10-01 20:39 ` [RFC PATCH 19/22] x86/fpu/amx: Define AMX state components and have it used for boot-time checks Chang S. Bae
2020-10-01 20:39 ` [RFC PATCH 20/22] x86/fpu/amx: Enable the AMX feature in 64-bit mode Chang S. Bae
2020-10-01 20:39 ` [RFC PATCH 21/22] selftest/x86/amx: Include test cases for the AMX state management Chang S. Bae
2020-10-01 20:39 ` [RFC PATCH 22/22] x86/fpu/xstate: Introduce boot-parameters for control some state component support Chang S. Bae
2020-10-02  2:09   ` Randy Dunlap
2020-10-13 23:00     ` Brown, Len
2020-10-02 17:15   ` Andy Lutomirski
2020-10-02 17:26     ` Dave Hansen
2020-10-13 23:38     ` Brown, Len
2020-10-02 17:25   ` Dave Hansen

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