From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-crypto <linux-crypto@vger.kernel.org>,
ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
Alexander Graf <graf@amazon.com>,
Mika Westerberg <mika.westerberg@linux.intel.com>,
Hans de Goede <hdegoede@redhat.com>, Len Brown <lenb@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH 2/3 v6] ACPI: allow longer device IDs
Date: Mon, 28 Feb 2022 23:27:08 +0200 [thread overview]
Message-ID: <Yh0+LA8B1jw8tnl9@smile.fi.intel.com> (raw)
In-Reply-To: <CAMj1kXFmEAKJRHCiuXyGECCmOs0+xX9AVeBDxfuD0XuX2TQ2Uw@mail.gmail.com>
On Mon, Feb 28, 2022 at 10:02:43PM +0100, Ard Biesheuvel wrote:
> On Mon, 28 Feb 2022 at 21:47, Andy Shevchenko <andy.shevchenko@gmail.com> wrote:
> >
> > On Mon, Feb 28, 2022 at 9:28 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
> > >
> > > From: Alexander Graf <graf@amazon.com>
> > >
> > > We create a list of ACPI "PNP" IDs which contains _HID, _CID, and CLS
> > > entries of the respective devices. However, when making structs for
> > > matching, we squeeze those IDs into acpi_device_id, which only has 9
> > > bytes space to store the identifier. The subsystem actually captures the
> > > full length of the IDs, and the modalias has the full length, but this
> > > struct we use for matching is limited. It originally had 16 bytes, but
> > > was changed to only have 9 in 6543becf26ff ("mod/file2alias: make
> > > modalias generation safe for cross compiling"), presumably on the theory
> > > that it would match the ACPI spec so it didn't matter.
> >
> > > Unfortunately, while most people adhere to the ACPI specs, Microsoft
> > > decided that its VM Generation Counter device [1] should only be
> > > identifiable by _CID with a value of "VM_Gen_Counter", which is longer
> > > than 9 characters.
> >
> > Then why do we not see the ECR from somebody to update the spec or to
> > fix MS' abuse of it?
> > I believe _this_ should be the prerequisite to the proposed change.
>
> What exactly are you suggesting here? That the contributor of this
> patch joins the UEFI forum as an individual adopter in order to get
> the ACPI spec updated before we can advance with this patch? Or that
> he works with Microsoft to get them to refrain from violating it?
>
> I don't think that is reasonable or realistic. The kernel is already
> riddled with UEFI and ACPI quirks that are only there because some
> teams at MS don't take the ACPI spec too literally (which is why they
> have their own AML compiler, for one), and PC vendors only care about
> the Windows sticker, so they don't care about the ACPI spec either.
>
> So I don't think this is the right time to get pedantic about this.
> Our ACPI subsystem already deals with CIDs that are longer than 8
> characters (which are btw permitted by the ACPI spec for bus topology
> related metadata), the only thing being changed here is the ability to
> actually match against such identifiers.
My point is that this is clear abuse of the spec and:
1) we have to enable the broken, because it is already in the wild with
the comment that this is an issue
AND
2) issue an ECR / work with MS to make sure they understand the problem.
This can be done in parallel. What I meant as a prerequisite is to start doing
2) while we have 1) on table.
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2022-02-28 21:28 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-26 22:06 [PATCH v5 0/3] ACPI: VM fork detection for RNG Jason A. Donenfeld
2022-02-26 22:06 ` [PATCH v5 1/3] random: add mechanism for VM forks to reinitialize crng Jason A. Donenfeld
2022-02-26 22:06 ` [PATCH v5 2/3] ACPI: allow longer device IDs Jason A. Donenfeld
2022-02-27 7:31 ` Ard Biesheuvel
2022-02-27 7:37 ` Ard Biesheuvel
2022-02-27 10:03 ` Jason A. Donenfeld
2022-02-27 10:30 ` Ard Biesheuvel
2022-02-27 10:47 ` Ard Biesheuvel
2022-02-27 11:38 ` Alexander Graf
2022-02-27 11:43 ` Ard Biesheuvel
2022-02-27 11:48 ` Alexander Graf
2022-02-27 11:59 ` Ard Biesheuvel
2022-02-27 11:42 ` Alexander Graf
2022-02-27 12:43 ` Jason A. Donenfeld
2022-02-27 23:27 ` Jason A. Donenfeld
2022-02-28 18:19 ` Rafael J. Wysocki
2022-02-28 18:21 ` Jason A. Donenfeld
2022-02-28 18:33 ` [PATCH 2/3 v6] " Jason A. Donenfeld
2022-02-28 20:46 ` Andy Shevchenko
2022-02-28 20:58 ` Jason A. Donenfeld
2022-02-28 21:02 ` Ard Biesheuvel
2022-02-28 21:27 ` Andy Shevchenko [this message]
2022-02-28 21:54 ` Jason A. Donenfeld
2022-02-28 22:14 ` Michael Kelley (LINUX)
2022-02-28 22:17 ` Jason A. Donenfeld
2022-02-28 22:21 ` Ard Biesheuvel
2022-02-28 22:38 ` Michael Kelley (LINUX)
2022-02-28 22:46 ` Ard Biesheuvel
2022-03-22 19:58 ` Michael Kelley (LINUX)
2022-03-22 20:11 ` Jason A. Donenfeld
2022-03-24 19:25 ` Michael Kelley (LINUX)
2022-03-22 22:06 ` Ard Biesheuvel
2022-03-24 19:24 ` Michael Kelley (LINUX)
2022-03-24 19:45 ` Jason A. Donenfeld
2022-03-24 20:14 ` Michael Kelley (LINUX)
2022-03-01 13:12 ` Andy Shevchenko
2022-02-28 22:00 ` Alexander Graf
2022-02-28 22:17 ` Ard Biesheuvel
2022-03-01 10:35 ` Hans de Goede
2022-03-01 10:38 ` Jason A. Donenfeld
2022-03-01 10:49 ` Hans de Goede
2022-03-01 14:25 ` Andy Shevchenko
2022-03-01 14:48 ` Jason A. Donenfeld
2022-03-01 12:29 ` Rafael J. Wysocki
2022-03-01 10:31 ` [PATCH v5 2/3] " Hans de Goede
2022-02-26 22:06 ` [PATCH v5 3/3] virt: vmgenid: introduce driver for reinitializing RNG on VM fork Jason A. Donenfeld
2022-03-06 16:02 ` Michael Kelley (LINUX)
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