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From: Will Deacon <will.deacon@arm.com>
To: Julien Grall <julien.grall@arm.com>
Cc: aou@eecs.berkeley.edu, Marc Zyngier <marc.zyngier@arm.com>,
	catalin.marinas@arm.com, Anup Patel <anup.Patel@wdc.com>,
	Palmer Dabbelt <palmer@sifive.com>,
	linux-kernel@vger.kernel.org, rppt@linux.ibm.com,
	hch@infradead.org, Atish.Patra@wdc.com,
	Guo Ren <guoren@kernel.org>,
	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 10:12:19 +0100
Message-ID: <20190619091219.GB7767@fuggles.cambridge.arm.com> (raw)
In-Reply-To: <c871a5ae-914f-a8bb-9474-1dcfec5d45bf@arm.com>

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

Will
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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 [this message]
2019-06-19 12:18           ` Guo Ren
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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