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

From: Guo Ren <guoren@kernel.org>
To: Anup Patel <Anup.Patel@wdc.com>
Cc: "julien.thierry@arm.com" <julien.thierry@arm.com>,
	"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
	Palmer Dabbelt <palmer@sifive.com>,
	Will Deacon <will.deacon@arm.com>,
	"christoffer.dall@arm.com" <christoffer.dall@arm.com>,
	Atish Patra <Atish.Patra@wdc.com>,
	"julien.grall@arm.com" <julien.grall@arm.com>,
	"gary@garyguo.net" <gary@garyguo.net>,
	"linux-riscv@lists.infradead.org"
	<linux-riscv@lists.infradead.org>, Will Deacon <will@kernel.org>,
	"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
	"rppt@linux.ibm.com" <rppt@linux.ibm.com>,
	"aou@eecs.berkeley.edu" <aou@eecs.berkeley.edu>,
	Arnd Bergmann <arnd@arndb.de>,
	"suzuki.poulose@arm.com" <suzuki.poulose@arm.com>,
	"marc.zyngier@arm.com" <marc.zyngier@arm.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
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	<iommu@lists.linux-foundation.org>,
	"james.morse@arm.com" <james.morse@arm.com>
Subject: Re: [PATCH RFC 11/14] arm64: Move the ASID allocator code in a separate file
Date: Thu, 19 Sep 2019 21:36:58 +0800	[thread overview]
Message-ID: <CAJF2gTRu4cSPd09mXkUOxnL2HO0wnAzqeVr3a3He0AFGCFD00g@mail.gmail.com> (raw)
In-Reply-To: <MN2PR04MB60612846CD50ED157DE5AB548D8F0@MN2PR04MB6061.namprd04.prod.outlook.com>

Hi,

On Tue, Sep 17, 2019 at 11:42 AM Anup Patel <Anup.Patel@wdc.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@wdc.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/
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