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From: Qais Yousef <qais.yousef@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Morten Rasmussen <morten.rasmussen@arm.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	James Morse <james.morse@arm.com>,
	linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org
Subject: Re: [RFC PATCH v2 4/4] arm64: Export id_aar64fpr0 via sysfs
Date: Thu, 22 Oct 2020 15:34:18 +0100	[thread overview]
Message-ID: <20201022143418.utd6vfl7ii3essal@e107158-lin> (raw)
In-Reply-To: <20201022143102.GH1229@gaia>

On 10/22/20 15:31, Catalin Marinas wrote:
> On Thu, Oct 22, 2020 at 03:55:59PM +0200, Greg Kroah-Hartman wrote:
> > On Thu, Oct 22, 2020 at 02:47:52PM +0100, Qais Yousef wrote:
> > > On 10/21/20 15:41, Will Deacon wrote:
> > > > > We already expose MIDR and REVIDR via the current sysfs interface. We
> > > > > can expand it to include _all_ the other ID_* regs currently available
> > > > > to user via the MRS emulation and we won't have to debate what a new
> > > > > interface would look like. The MRS emulation and the sysfs info should
> > > > > probably match, though that means we need to expose the
> > > > > ID_AA64PFR0_EL1.EL0 field which we currently don't.
> > > > > 
> > > > > I do agree that an AArch32 cpumask is an easier option both from the
> > > > > kernel implementation perspective and from the application usability
> > > > > one, though not as easy as automatic task placement by the scheduler (my
> > > > > first preference, followed by the id_* regs and the aarch32 mask, though
> > > > > not a strong preference for any).
> > > > 
> > > > If a cpumask is easier to implement and easier to use, then I think that's
> > > > what we should do. It's also then dead easy to disable if necessary by
> > > > just returning 0. The only alternative I would prefer is not having to
> > > > expose this information altogether, but I'm not sure that figuring this
> > > > out from MIDR/REVIDR alone is reliable.
> > > 
> > > So the mask idea is about adding a new
> > > 
> > > 	/sys/devices/system/cpu/aarch32_cpus
> > > 
> > > ?
> > 
> > Is this a file, a directory, or what?  What's the contents?
> > 
> > Without any of that, I have no idea if it's "ok" or not...
> 
> I don't know what Qais thinks but a file matching the syntax of the
> present/online/offline/possible files (e.g. 0-3) would look more
> consistent.

Yes. Sorry I thought it's obvious.

Thanks

--
Qais Yousef

  reply	other threads:[~2020-10-22 14:34 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-21 10:46 [RFC PATCH v2 0/4] Add support for Asymmetric AArch32 systems Qais Yousef
2020-10-21 10:46 ` [RFC PATCH v2 1/4] arm64: kvm: Handle " Qais Yousef
2020-10-21 12:02   ` Marc Zyngier
2020-10-21 13:35     ` Qais Yousef
2020-10-21 13:51       ` Marc Zyngier
2020-10-21 14:38         ` Qais Yousef
2020-11-02 17:58         ` Qais Yousef
2020-10-21 10:46 ` [RFC PATCH v2 2/4] arm64: Add support for asymmetric AArch32 EL0 configurations Qais Yousef
2020-10-21 15:39   ` Will Deacon
2020-10-21 16:21     ` Qais Yousef
2020-10-21 16:52       ` Catalin Marinas
2020-10-21 17:39         ` Will Deacon
2020-10-22  9:53           ` Catalin Marinas
2020-10-21 10:46 ` [RFC PATCH v2 3/4] arm64: export emulate_sys_reg() Qais Yousef
2020-10-21 10:46 ` [RFC PATCH v2 4/4] arm64: Export id_aar64fpr0 via sysfs Qais Yousef
2020-10-21 11:09   ` Marc Zyngier
2020-10-21 11:25     ` Greg Kroah-Hartman
2020-10-21 11:46       ` Marc Zyngier
2020-10-21 12:11         ` Greg Kroah-Hartman
2020-10-21 13:18         ` Qais Yousef
2020-10-21 12:15     ` Catalin Marinas
2020-10-21 13:20       ` Qais Yousef
2020-10-21 13:33       ` Morten Rasmussen
2020-10-21 14:09         ` Catalin Marinas
2020-10-21 14:41           ` Morten Rasmussen
2020-10-21 14:45           ` Will Deacon
2020-10-21 15:10             ` Catalin Marinas
2020-10-21 15:37               ` Will Deacon
2020-10-21 16:18                 ` Catalin Marinas
2020-10-21 17:19                   ` Will Deacon
2020-10-22  9:55                     ` Morten Rasmussen
2020-10-21 14:31         ` Qais Yousef
2020-10-22 10:16           ` Morten Rasmussen
2020-10-22 10:48             ` Qais Yousef
2020-10-21 14:41       ` Will Deacon
2020-10-21 15:03         ` Qais Yousef
2020-10-21 15:23           ` Will Deacon
2020-10-21 16:07             ` Qais Yousef
2020-10-21 17:23               ` Will Deacon
2020-10-21 19:57                 ` Qais Yousef
2020-10-21 20:26                   ` Will Deacon
2020-10-22  8:16                     ` Catalin Marinas
2020-10-22  9:58                       ` Qais Yousef
2020-10-22 13:47         ` Qais Yousef
2020-10-22 13:55           ` Greg Kroah-Hartman
2020-10-22 14:31             ` Catalin Marinas
2020-10-22 14:34               ` Qais Yousef [this message]
2020-10-26 19:02             ` Qais Yousef
2020-10-26 19:08               ` Greg Kroah-Hartman
2020-10-26 19:18                 ` Qais Yousef
2020-10-21 11:28   ` Greg Kroah-Hartman
2020-10-21 13:22     ` Qais Yousef
2020-10-21 11:26 ` [RFC PATCH v2 0/4] Add support for Asymmetric AArch32 systems Greg Kroah-Hartman
2020-10-21 13:15   ` Qais Yousef
2020-10-21 13:31     ` Greg Kroah-Hartman
2020-10-21 13:55       ` Qais Yousef
2020-10-21 14:35       ` Catalin Marinas

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