linux-kernel - Re: [RFT PATCH v3 12/27] of/address: Add infrastructure to declare MMIO as non-posted

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAL_JsqK200WcxD3PP1FToc5w2dyF3b6TYnf2oNd9Mpz77g68og@mail.gmail.com>
Date:   Thu, 11 Mar 2021 11:10:20 -0700
From:   Rob Herring <robh@...nel.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Hector Martin <marcan@...can.st>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Marc Zyngier <maz@...nel.org>, Olof Johansson <olof@...om.net>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Mark Kettenis <mark.kettenis@...all.nl>,
        Tony Lindgren <tony@...mide.com>,
        Mohamed Mediouni <mohamed.mediouni@...amail.com>,
        Stan Skowronek <stan@...ellium.com>,
        Alexander Graf <graf@...zon.com>,
        Will Deacon <will@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Corbet <corbet@....net>,
        Catalin Marinas <catalin.marinas@....com>,
        Christoph Hellwig <hch@...radead.org>,
        "David S. Miller" <davem@...emloft.net>,
        DTML <devicetree@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
        "open list:GENERIC INCLUDE/ASM HEADER FILES" 
        <linux-arch@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFT PATCH v3 12/27] of/address: Add infrastructure to declare
 MMIO as non-posted

On Thu, Mar 11, 2021 at 9:48 AM Arnd Bergmann <arnd@...nel.org> wrote:
>
> On Thu, Mar 11, 2021 at 5:10 PM Rob Herring <robh@...nel.org> wrote:
> > On Thu, Mar 11, 2021 at 2:12 AM Arnd Bergmann <arnd@...nel.org> wrote:
> > > On Wed, Mar 10, 2021 at 6:01 PM Rob Herring <robh@...nel.org> wrote:
> > > Ok, makes sense.
> > >
> > > Conceptually, I'd like to then see a check that verifies that the
> > > property is only set for nodes whose parent also has it set, since
> > > that is how AXI defines it: A bus can wait for the ack from its
> > > child node, or it can acknowledge the write to its parent early.
> > > However, this breaks down as soon as a bus does the early ack:
> > > all its children by definition use posted writes (as seen by the
> > > CPU), even if they wait for stores that come from other masters.
> > >
> > > Does this make sense to you?
> >
> > BTW, I don't think it's clear in this thread, but the current
> > definition proposed for the spec[1] and schema is 'nonposted-mmio' is
> > specific to 'simple-bus'. I like this restriction and we can expand
> > where 'nonposted-mmio' is allowed later if needed.
>
> That sounds ok, as long as we can express everything for the mac
> at the moment. Do we need to explicitly add a description to allow
> the property in the root node in addition to simple-bus to be able
> to enforce the rule about parent buses also having it?

IMO it should not be allowed in the root node. That's a failure to
define a bus node. Also, would that mean your memory has to be
non-posted!?

Rob