Date:   Mon, 20 Mar 2023 11:00:48 -0700
From:   Darren Hart <darren@os.amperecomputing.com>
To:     Ard Biesheuvel <ardb@kernel.org>
Cc:     Andrea Righi <andrea.righi@canonical.com>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Paolo Pisati <paolo.pisati@canonical.com>,
        linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: kernel 6.2 stuck at boot (efi_call_rts) on arm64
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On Sat, Mar 18, 2023 at 11:35:44AM +0100, Ard Biesheuvel wrote:
> On Thu, 16 Mar 2023 at 23:28, Darren Hart <darren@os.amperecomputing.com> wrote:
> >
> > On Thu, Mar 16, 2023 at 07:55:36PM +0100, Ard Biesheuvel wrote:
> > > On Thu, 16 Mar 2023 at 18:52, Andrea Righi <andrea.righi@canonical.com> wrote:
> ...
> > > >
> > > > Yay! Success! I just tested your latest efi/urgent (with the fixup) and
> > > > system completed the boot without any soft lockups.
> > > >
> > >
> > > Thanks for confirming. I'll take that as a tested-by
> >
> > The solution in the current branch looks like the best approach we have to date
> > to address the broadest of affected systems. We could switch the eMAG test to an
> > MIDR test I believe (but this won't work for Altra as that would capture all the
> > Neoverse v1 cores beyond Altra). I can look into the MIDR test if you think it's
> > worthwhile - but since I don't think we can eliminate the SMBIOS string test, it
> > doesn't buy us much since we don't need a greedier eMAG test (there aren't more
> > of them to match).
> >
> > Given that some OEM Altra platforms change the processor ID, I don't see a
> > better solution currently than adding their the "product name" to the smbios
> > string tests unfortunately.
> >
> 
> Indeed. I spotted a Gigabyte system [0] with a different processor ID,
> but with a version we can test for.
> 
> So for now, I'll go with
> 
>         socid = (u32 *)record->processor_id;
>         switch (*socid & 0xffff000f) {
>                 static char const altra[] = "Ampere(TM) Altra(TM) Processor";
>                 static char const emag[] = "eMAG";
>         default:
>                 version = efi_get_smbios_string(&record->header, 4,
>                                                 processor_version);
>                 if (!version || (strncmp(version, altra, sizeof(altra) - 1) &&
>                                  strncmp(version, emag, sizeof(emag) - 1)))
>                         break;
> 
>                 fallthrough;
> 
>         case 0x0a160001:        // Altra
>         case 0x0a160002:        // Altra Max
>                 efi_warn("Working around broken SetVirtualAddressMap()\n");
> ...
> 
> which should cover all the affected systems we encountered so far.
> 
> I'll push this to linux-next to let it soak for a little bit, and then
> send it to Linus somewhere during the week

Thank you Ard, I think this is our best option.

-- 
Darren Hart
Ampere Computing / OS and Kernel