linux-kernel - Re: [PATCH v3 RESEND] acpi,pci: warn about duplicate IRQ routing entries returned from

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: <20230123214414.GA987407@bhelgaas>
Date:   Mon, 23 Jan 2023 15:44:14 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Mateusz Jończyk <mat.jonczyk@...pl>
Cc:     linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-i2c@...r.kernel.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>, Borislav Petkov <bp@...e.de>,
        Jean Delvare <jdelvare@...e.com>,
        Jean Delvare <jdelvare@...e.de>
Subject: Re: [PATCH v3 RESEND] acpi,pci: warn about duplicate IRQ routing
 entries returned from _PRT

On Mon, Jan 23, 2023 at 10:00:43PM +0100, Mateusz Jończyk wrote:
> W dniu 23.01.2023 o 21:33, Bjorn Helgaas pisze:
> > On Sat, Jan 21, 2023 at 04:33:14PM +0100, Mateusz Jończyk wrote:
> >> On some platforms, the ACPI _PRT function returns duplicate interrupt
> >> routing entries. Linux uses the first matching entry, but sometimes the
> >> second matching entry contains the correct interrupt vector.
> >>
> >> Print an error to dmesg if duplicate interrupt routing entries are
> >> present, so that we could check how many models are affected.
> >
> > It shouldn't be too hard to use qemu to figure out whether Windows
> > uses the last matching entry, i.e., treating _PRT entries as
> > assignments.  If so, maybe Linux could just do the same.
> >
> > Is anybody up for that?
> 
> The hardware in question has a working Windows XP installation,
> and I could in theory check which interrupt vector it uses - but
> I think that such reverse engineering is forbidden by Windows' EULA.

I'm not talking about any sort of disassembly or anything like that;
just that we can observe what Windows does given the _PRT contents.
You've already figured out that on your particular hardware, the _PRT
has two entries, and Linux uses the first one while Windows uses the
second one, right?

On qemu, we have control over the BIOS and can easily update _PRT to
whatever we want, and then we could boot Windows and see what it uses.
But I guess maybe that wouldn't tell us anything more than what you
already discovered.

So my inclination would be to make Linux use the last matching entry.

Bjorn