linux-kernel - Re: [PATCH] arm64: efi: Force the use of SetVirtualAddressMap() on Altra Max machines

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Date:   Thu, 9 Feb 2023 00:44:35 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Darren Hart <darren@...amperecomputing.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, stable@...r.kernel.org,
        linux-efi@...r.kernel.org,
        Alexandru Elisei <alexandru.elisei@...il.com>
Subject: Re: [PATCH] arm64: efi: Force the use of SetVirtualAddressMap() on
 Altra Max machines

On Thu, 9 Feb 2023 at 00:43, Darren Hart <darren@...amperecomputing.com> wrote:
>
> On Thu, Feb 09, 2023 at 12:16:46AM +0100, Ard Biesheuvel wrote:
> > Hello Darren,
> >
> > On Thu, 9 Feb 2023 at 00:14, Darren Hart <darren@...amperecomputing.com> wrote:
> > >
> > > Commit 550b33cfd445 ("arm64: efi: Force the use of SetVirtualAddressMap()
> > > on Altra machines") identifies the Altra family via the family field in
> > > the type#1 SMBIOS record. Altra Max machines are similarly affected but
> > > not detected with the strict strcmp test.
> > >
> > > Rather than risk greedy matching with strncmp, add a second test for
> > > Altra Max. Do not refactor to handle multiple tests as these should be
> > > the only two needed.
> > >
> >
> > Famous last words ...
>
> Indeed, I nearly included that myself...
>
> >
> > Unfortunately, I just had a report the other day that 'eMAG' and
> > 'Server' (!) are also being used.
> >
> > https://lore.kernel.org/all/20230131040355.3116-1-justin.he@arm.com/
> >
>
> OK, so in order to workaround this in the kernel, we need a better way to match.
> Unfortunately, this is specific to the oem platform, and the oem controls those
> strings.
>
> Thanks for the pointer, will go mull this over and see if I can come up with
> something better.
>
> In the meantime, would you consider matching on:
> Altra
> Altra Max
> eMAG
>
> to capture the bulk of the systems until we have a better solution?
>

Yeah that's fine.