linux-kernel - Re: qemu-arm64: handle_futex_death - kernel/futex/core.c:661 - Unable to handle kernel unknown 43 at virtual address

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Date:   Sat, 28 Oct 2023 09:42:27 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Naresh Kamboju <naresh.kamboju@...aro.org>
Cc:     Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Linux-Next Mailing List <linux-next@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        lkft-triage@...ts.linaro.org, Arnd Bergmann <arnd@...db.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Anders Roxell <anders.roxell@...aro.org>,
        Dan Carpenter <dan.carpenter@...aro.org>,
        LTP List <ltp@...ts.linux.it>, Petr Vorel <pvorel@...e.cz>
Subject: Re: qemu-arm64: handle_futex_death - kernel/futex/core.c:661 - Unable
 to handle kernel unknown 43 at virtual address

On Fri, 27 Oct 2023 at 12:57, Naresh Kamboju <naresh.kamboju@...aro.org> wrote:
>
> On Thu, 26 Oct 2023 at 21:09, Ard Biesheuvel <ardb@...nel.org> wrote:
> >
> > On Thu, 26 Oct 2023 at 17:30, Mark Rutland <mark.rutland@....com> wrote:
> > >
> > > On Thu, Oct 26, 2023 at 08:11:26PM +0530, Naresh Kamboju wrote:
> > > > Following kernel crash noticed on qemu-arm64 while running LTP syscalls
> > > > set_robust_list test case running Linux next 6.6.0-rc7-next-20231026 ...
> > > It looks like this is fallout from the LPA2 enablement.
> > >
> > > According to the latest ARM ARM (ARM DDI 0487J.a), page D19-6475, that "unknown
> > > 43" (0x2b / 0b101011) is the DFSC for a level -1 translation fault:
> > >
> > >         0b101011 When FEAT_LPA2 is implemented:
> > >                  Translation fault, level -1.
> > >
> > > It's triggered here by an LDTR in a get_user() on a bogus userspace address.
> > > The exception is expected, and it's supposed to be handled via the exception
> > > fixups, but the LPA2 patches didn't update the fault_info table entries for all
> > > the level -1 faults, and so those all get handled by do_bad() and don't call
> > > fixup_exception(), causing them to be fatal.
> > >
> > > It should be relatively simple to update the fault_info table for the level -1
> > > faults, but given the other issues we're seeing I think it's probably worth
> > > dropping the LPA2 patches for the moment.
> > >
> >
> > Thanks for the analysis Mark.
> >
> > I agree that this should not be difficult to fix, but given the other
> > CI problems and identified loose ends, I am not going to object to
> > dropping this partially or entirely at this point. I'm sure everybody
> > will be thrilled to go over those 60 patches again after I rebase them
> > onto v6.7-rc1 :-)
>
> I am happy to test any proposed fix patch.
>

Thanks Naresh. Patch attached.

View attachment "0001-Add-missing-ESR-decoding-for-level-1-translation-fau.patch" of type "text/x-patch" (2659 bytes)