From: Palmer Dabbelt <palmer@sifive.com>
To: will@kernel.org
Cc: julien.thierry@arm.com, catalin.marinas@arm.com,
Will Deacon <will.deacon@arm.com>,
christoffer.dall@arm.com, Atish Patra <Atish.Patra@wdc.com>,
julien.grall@arm.com, guoren@kernel.org, gary@garyguo.net,
linux-riscv@lists.infradead.org, kvmarm@lists.cs.columbia.edu,
rppt@linux.ibm.com, Christoph Hellwig <hch@infradead.org>,
aou@eecs.berkeley.edu, Arnd Bergmann <arnd@arndb.de>,
suzuki.poulose@arm.com, marc.zyngier@arm.com,
Paul Walmsley <paul.walmsley@sifive.com>,
linux-arm-kernel@lists.infradead.org,
Anup Patel <Anup.Patel@wdc.com>,
linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
james.morse@arm.com
Subject: Re: [PATCH RFC 11/14] arm64: Move the ASID allocator code in a separate file
Date: Mon, 16 Sep 2019 11:28:58 -0700 (PDT) [thread overview]
Message-ID: <mhng-11e0cc7f-264b-4412-9424-2357bc27dcb3@palmer-si-x1c4> (raw)
In-Reply-To: <20190916181800.7lfpt3t627byoomt@willie-the-truck>
On Mon, 16 Sep 2019 11:18:00 PDT (-0700), will@kernel.org wrote:
> On Sun, Sep 15, 2019 at 05:03:38AM +0000, Anup Patel wrote:
>>
>>
>> > -----Original Message-----
>> > From: linux-kernel-owner@vger.kernel.org <linux-kernel-
>> > owner@vger.kernel.org> On Behalf Of Palmer Dabbelt
>> > Sent: Saturday, September 14, 2019 7:31 PM
>> > To: will@kernel.org
>> > Cc: guoren@kernel.org; Will Deacon <will.deacon@arm.com>;
>> > julien.thierry@arm.com; aou@eecs.berkeley.edu; james.morse@arm.com;
>> > Arnd Bergmann <arnd@arndb.de>; suzuki.poulose@arm.com;
>> > marc.zyngier@arm.com; catalin.marinas@arm.com; Anup Patel
>> > <Anup.Patel@wdc.com>; linux-kernel@vger.kernel.org;
>> > rppt@linux.ibm.com; Christoph Hellwig <hch@infradead.org>; Atish Patra
>> > <Atish.Patra@wdc.com>; julien.grall@arm.com; gary@garyguo.net; Paul
>> > Walmsley <paul.walmsley@sifive.com>; christoffer.dall@arm.com; linux-
>> > riscv@lists.infradead.org; kvmarm@lists.cs.columbia.edu; linux-arm-
>> > kernel@lists.infradead.org; iommu@lists.linux-foundation.org
>> > Subject: Re: [PATCH RFC 11/14] arm64: Move the ASID allocator code in a
>> > separate file
>> >
>> > On Thu, 12 Sep 2019 07:02:56 PDT (-0700), will@kernel.org wrote:
>> > > On Sun, Sep 08, 2019 at 07:52:55AM +0800, Guo Ren wrote:
>> > >> On Mon, Jun 24, 2019 at 6:40 PM Will Deacon <will@kernel.org> wrote:
>> > >> > > I'll keep my system use the same ASID for SMP + IOMMU :P
>> > >> >
>> > >> > You will want a separate allocator for that:
>> > >> >
>> > >> > https://lkml.kernel.org/r/20190610184714.6786-2-jean-philippe.bruck
>> > >> > er@arm.com
>> > >>
>> > >> Yes, it is hard to maintain ASID between IOMMU and CPUMMU or
>> > >> different system, because it's difficult to synchronize the IO_ASID
>> > >> when the CPU ASID is rollover.
>> > >> But we could still use hardware broadcast TLB invalidation
>> > >> instruction to uniformly manage the ASID and IO_ASID, or OTHER_ASID in
>> > our IOMMU.
>> > >
>> > > That's probably a bad idea, because you'll likely stall execution on
>> > > the CPU until the IOTLB has completed invalidation. In the case of
>> > > ATS, I think an endpoint ATC is permitted to take over a minute to
>> > > respond. In reality, I suspect the worst you'll ever see would be in
>> > > the msec range, but that's still an unacceptable period of time to hold a
>> > CPU.
>> > >
>> > >> Welcome to join our disscusion:
>> > >> "Introduce an implementation of IOMMU in linux-riscv"
>> > >> 9 Sep 2019, 10:45 Jade-room-I&II (Corinthia Hotel Lisbon) RISC-V MC
>> > >
>> > > I attended this session, but it unfortunately raised many more
>> > > questions than it answered.
>> >
>> > Ya, we're a long way from figuring this out.
>>
>> For everyone's reference, here is our first attempt at RISC-V ASID allocator:
>> http://archive.lwn.net:8080/linux-kernel/20190329045111.14040-1-anup.patel@wdc.com/T/#u
>
> With a reply stating that the patch "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.
>
> Seriously, they say "walk before you can run", but this is more "crawl
> before you can fly". What's the rush?
I agree, and I think I've been pretty clear here: we're not merging this ASID
stuff until we have a platform we can test on, particularly as the platforms we
have now already need some wacky hacks around TLB flushing that we haven't
gotten to the bottom of.
> Will
_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv
next prev parent reply other threads:[~2019-09-16 18:29 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190321163623.20219-1-julien.grall@arm.com>
[not found] ` <20190321163623.20219-12-julien.grall@arm.com>
2019-06-05 16:56 ` [PATCH RFC 11/14] arm64: Move the ASID allocator code in a separate file 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
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
[not found] ` <CAJF2gTTsHCsSpf1ncVb=ZJS2d=r+AdDi2=5z-REVS=uUg9138A@mail.gmail.com>
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 [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=mhng-11e0cc7f-264b-4412-9424-2357bc27dcb3@palmer-si-x1c4 \
--to=palmer@sifive.com \
--cc=Anup.Patel@wdc.com \
--cc=Atish.Patra@wdc.com \
--cc=aou@eecs.berkeley.edu \
--cc=arnd@arndb.de \
--cc=catalin.marinas@arm.com \
--cc=christoffer.dall@arm.com \
--cc=gary@garyguo.net \
--cc=guoren@kernel.org \
--cc=hch@infradead.org \
--cc=iommu@lists.linux-foundation.org \
--cc=james.morse@arm.com \
--cc=julien.grall@arm.com \
--cc=julien.thierry@arm.com \
--cc=kvmarm@lists.cs.columbia.edu \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-riscv@lists.infradead.org \
--cc=marc.zyngier@arm.com \
--cc=paul.walmsley@sifive.com \
--cc=rppt@linux.ibm.com \
--cc=suzuki.poulose@arm.com \
--cc=will.deacon@arm.com \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).