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From: Guo Ren <guoren@kernel.org>
To: Arnd Bergmann <arnd@arndb.de>, Will Deacon <will.deacon@arm.com>
Cc: aou@eecs.berkeley.edu, Marc Zyngier <marc.zyngier@arm.com>,
	catalin.marinas@arm.com, Anup Patel <anup.Patel@wdc.com>,
	linux-kernel@vger.kernel.org, rppt@linux.ibm.com,
	hch@infradead.org, Atish.Patra@wdc.com,
	Julien Grall <julien.grall@arm.com>,
	Palmer Dabbelt <palmer@sifive.com>,
	gary@garyguo.net, paul.walmsley@sifive.com,
	linux-riscv@lists.infradead.org, kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH RFC 11/14] arm64: Move the ASID allocator code in a separate file
Date: Wed, 19 Jun 2019 20:18:04 +0800
Message-ID: <CAJF2gTTmFq3yYa9UrdZRAFwJgC=KmKTe2_NFy_UZBUQovqQJPg@mail.gmail.com> (raw)
In-Reply-To: <20190619091219.GB7767@fuggles.cambridge.arm.com>

On Wed, Jun 19, 2019 at 5:12 PM Will Deacon <will.deacon@arm.com> wrote:
>
> On Wed, Jun 19, 2019 at 09:54:21AM +0100, Julien Grall wrote:
> > On 6/19/19 9:07 AM, Guo Ren wrote:
> > > You forgot CCing C-SKY folks :P
> >
> > I wasn't aware you could be interested :).
> >
> > > Move arm asid allocator code in a generic one is a agood idea, I've
> > > made a patchset for C-SKY and test is on processing, See:
> > > https://lore.kernel.org/linux-csky/1560930553-26502-1-git-send-email-guoren@kernel.org/
> > >
> > > If you plan to seperate it into generic one, I could co-work with you.
> >
> > Was the ASID allocator work out of box on C-Sky? If so, I can easily move
> > the code in a generic place (maybe lib/asid.c).
>
> This is one place where I'd actually prefer not to go down the route of
> making the code generic. Context-switching and low-level TLB management
> is deeply architecture-specific and I worry that by trying to make this
> code common, we run the real risk of introducing subtle bugs on some
> architecture every time it is changed.
"Add generic asid code" and "move arm's into generic" are two things.
We could do
first and let architecture's maintainer to choose.

> Furthermore, the algorithm we use
> on arm64 is designed to scale to large systems using DVM and may well be
> too complex and/or sub-optimal for architectures with different system
> topologies or TLB invalidation mechanisms.
It's just a asid algorithm not very complex and there is a callback
for architecture to define their
own local hart tlb flush. Seems it has nothing with DVM or tlb
broadcast mechanism.

>
> It's not a lot of code, so I don't see that it's a big deal to keep it
> under arch/arm64.
Yes, I think that's ok for arm64.

Hi Arnd,
What do you think about adding generic asid code for arch selection?

Best Regards
 Guo Ren
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Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-21 16:36 [PATCH RFC 00/14] kvm/arm: Align the VMID allocation with the arm64 ASID one Julien Grall
2019-03-21 16:36 ` [PATCH RFC 01/14] arm64/mm: Introduce asid_info structure and move asid_generation/asid_map to it Julien Grall
2019-03-21 17:03   ` Suzuki K Poulose
2019-03-21 17:27     ` Julien Grall
2019-03-21 16:36 ` [PATCH RFC 02/14] arm64/mm: Move active_asids and reserved_asids to asid_info Julien Grall
2019-03-21 16:36 ` [PATCH RFC 03/14] arm64/mm: Move bits " Julien Grall
2019-03-21 16:36 ` [PATCH RFC 04/14] arm64/mm: Move the variable lock and tlb_flush_pending " Julien Grall
2019-03-21 16:36 ` [PATCH RFC 05/14] arm64/mm: Remove dependency on MM in new_context Julien Grall
2019-03-21 16:36 ` [PATCH RFC 06/14] arm64/mm: Store the number of asid allocated per context Julien Grall
2019-03-21 16:36 ` [PATCH RFC 07/14] arm64/mm: Introduce NUM_ASIDS Julien Grall
2019-03-21 16:36 ` [PATCH RFC 08/14] arm64/mm: Split asid_inits in 2 parts Julien Grall
2019-03-21 16:36 ` [PATCH RFC 09/14] arm64/mm: Split the function check_and_switch_context in 3 parts Julien Grall
2019-03-21 16:36 ` [PATCH RFC 10/14] arm64/mm: Introduce a callback to flush the local context Julien Grall
2019-03-21 16:36 ` [PATCH RFC 11/14] arm64: Move the ASID allocator code in a separate file Julien Grall
2019-06-05 16:56   ` Julien Grall
2019-06-05 20:41     ` Palmer Dabbelt
2019-06-11  1:56       ` Gary Guo
2019-06-19  8:07     ` Guo Ren
2019-06-19  8:54       ` Julien Grall
2019-06-19  9:12         ` Will Deacon
2019-06-19 12:18           ` Guo Ren [this message]
2019-06-19 12:39             ` Will Deacon
2019-06-20  9:33               ` Guo Ren
2019-06-24 10:40                 ` Will Deacon
2019-06-25  7:25                   ` Palmer Dabbelt
2019-09-07 23:52                   ` Guo Ren
2019-09-12 14:02                     ` Will Deacon
2019-09-12 14:59                       ` Guo Ren
2019-09-13  7:13                         ` Guo Ren
2019-09-14  8:49                           ` Guo Ren
2019-09-16 12:57                           ` Jean-Philippe Brucker
2019-09-19 13:07                             ` Guo Ren
2019-09-19 15:18                               ` Jean-Philippe Brucker
2019-09-20  0:07                                 ` Guo Ren
2019-09-20  7:18                                   ` Jean-Philippe Brucker
2019-09-14 14:01                       ` Palmer Dabbelt
2019-09-15  5:03                         ` Anup Patel
2019-09-16 18:18                           ` Will Deacon
2019-09-16 18:28                             ` Palmer Dabbelt
2019-09-17  3:42                             ` Anup Patel
2019-09-19 13:36                               ` Guo Ren
2019-06-19 11:51         ` Guo Ren
2019-06-19 12:52           ` Julien Grall
2019-06-21 14:16           ` Catalin Marinas
2019-06-23 16:35             ` Guo Ren
2019-06-24 10:22               ` Will Deacon
2019-06-27  9:41                 ` qi.fuli
2019-06-27 10:26                   ` Will Deacon
2019-06-24 15:38               ` Catalin Marinas
2019-06-30  4:29                 ` Guo Ren
2019-07-01  9:17                   ` Catalin Marinas
2019-07-16  3:31                     ` Guo Ren
2019-07-22 16:38                       ` Catalin Marinas
2019-03-21 16:36 ` [PATCH RFC 12/14] arm64/lib: asid: Allow user to update the context under the lock Julien Grall
2019-03-21 16:36 ` [PATCH RFC 13/14] arm/kvm: Introduce a new VMID allocator Julien Grall
2019-03-21 16:36 ` [PATCH RFC 14/14] kvm/arm: Align the VMID allocation with the arm64 ASID one Julien Grall

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