linux-kernel - Re: [PATCH RFC 11/14] arm64: Move the ASID allocator code in a separate file

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Date:   Thu, 19 Sep 2019 21:36:58 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Anup Patel <Anup.Patel@....com>
Cc:     Will Deacon <will@...nel.org>, Palmer Dabbelt <palmer@...ive.com>,
        Will Deacon <will.deacon@....com>,
        "julien.thierry@....com" <julien.thierry@....com>,
        "aou@...s.berkeley.edu" <aou@...s.berkeley.edu>,
        "james.morse@....com" <james.morse@....com>,
        Arnd Bergmann <arnd@...db.de>,
        "suzuki.poulose@....com" <suzuki.poulose@....com>,
        "marc.zyngier@....com" <marc.zyngier@....com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "rppt@...ux.ibm.com" <rppt@...ux.ibm.com>,
        Christoph Hellwig <hch@...radead.org>,
        Atish Patra <Atish.Patra@....com>,
        "julien.grall@....com" <julien.grall@....com>,
        "gary@...yguo.net" <gary@...yguo.net>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        "christoffer.dall@....com" <christoffer.dall@....com>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "kvmarm@...ts.cs.columbia.edu" <kvmarm@...ts.cs.columbia.edu>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>
Subject: Re: [PATCH RFC 11/14] arm64: Move the ASID allocator code in a
 separate file

Hi,

On Tue, Sep 17, 2019 at 11:42 AM Anup Patel <Anup.Patel@....com> wrote:

> >
> > With a reply stating that the patch "absolutely does not work" ;)
>
> This patch was tested on existing HW (which does not have ASID implementation)
> and tested on QEMU (which has very simplistic Implementation of ASID).
>
> When I asked Gary Guo about way to get access to their HW (in same patch
> email thread), I did not get any reply. After so many months passed, I now
> doubt the his comment "absolutely does not work".
> >
> > What exactly do you want people to do with that? It's an awful lot of effort to
> > review this sort of stuff and given that Guo Ren is talking about sharing page
> > tables between the CPU and an accelerator, maybe you're better off
> > stabilising Linux for the platforms that you can actually test rather than
> > getting so far ahead of yourselves that you end up with a bunch of wasted
> > work on patches that probably won't get merged any time soon.
>
> The intention of the ASID patch was to encourage RISC-V implementations
> having ASID in HW and also ensure that things don't break on existing HW.
>
> I don't see our efforts being wasted in trying to make Linux RISC-V feature
> complete and encouraging more feature rich RISC-V CPUs.
>
> Delays in merging patches are fine as long as people have something to try
> on their RISC-V CPU implementations.
>
I'm the supporter of that patch:
http://archive.lwn.net:8080/linux-kernel/20190329045111.14040-1-anup.patel@....com/T/#u

Because it implicit hw broadcast tlb invalidation optimization.

Honestly it's not suitable for remote tlb flush with software IPI, but
it's still much better than current RISC-V's.

I'll try it on our hardware: 910. wait a moment :)

-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/