Message-ID: <DBBPR08MB4538F7FCCB0D05C1F2FCA853F7DE9@DBBPR08MB4538.eurprd08.prod.outlook.com>
Date:   Fri, 10 Feb 2023 02:38:26 +0000
From:   Justin He <Justin.He@....com>
To:     Darren Hart <darren@...amperecomputing.com>,
        Ard Biesheuvel <ardb@...nel.org>
CC:     LKML <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        Alexandru Elisei <alexandru.elisei@...il.com>, nd <nd@....com>,
        Nathan Chancellor <nathan@...nel.org>
Subject: RE: [PATCH v2] arm64: efi: Force the use of SetVirtualAddressMap() on
 eMAG and Altra Max machines

Hi Darren and Ard

> -----Original Message-----
> From: Darren Hart <darren@...amperecomputing.com>
> Sent: Friday, February 10, 2023 5:07 AM
> To: Ard Biesheuvel <ardb@...nel.org>
> Cc: Justin He <Justin.He@....com>; LKML <linux-kernel@...r.kernel.org>;
> stable@...r.kernel.org; linux-efi@...r.kernel.org; Alexandru Elisei
> <alexandru.elisei@...il.com>; nd <nd@....com>; Nathan Chancellor
> <nathan@...nel.org>
> Subject: Re: [PATCH v2] arm64: efi: Force the use of SetVirtualAddressMap() on
> eMAG and Altra Max machines
> 
> On Thu, Feb 09, 2023 at 04:30:57PM +0100, Ard Biesheuvel wrote:
> > (cc Nathan, another happy Ampere customer)
> >
> > On Thu, 9 Feb 2023 at 05:26, Justin He <Justin.He@....com> wrote:
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: Darren Hart <darren@...amperecomputing.com>
> > > > Sent: Thursday, February 9, 2023 8:28 AM
> > > > To: LKML <linux-kernel@...r.kernel.org>
> > > > Cc: stable@...r.kernel.org; linux-efi@...r.kernel.org; Alexandru
> > > > Elisei <alexandru.elisei@...il.com>; Justin He
> > > > <Justin.He@....com>; Huacai Chen <chenhuacai@...nel.org>; Jason A.
> > > > Donenfeld <Jason@...c4.com>; Ard Biesheuvel <ardb@...nel.org>
> > > > Subject: [PATCH v2] arm64: efi: Force the use of
> > > > SetVirtualAddressMap() on eMAG and Altra Max machines
> > > >
> > > > 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. eMAG and
> > > > Altra Max machines are similarly affected but not detected with the strict
> strcmp test.
> > > >
> > > > The type1_family smbios string is not an entirely reliable means
> > > > of identifying systems with this issue as OEMs can, and do, use
> > > > their own strings for these fields. However, until we have a
> > > > better solution, capture the bulk of these systems by adding strcmp
> matching for "eMAG"
> > > > and "Altra Max".
> > > >
> > > > Fixes: 550b33cfd445 ("arm64: efi: Force the use of
> > > > SetVirtualAddressMap() on Altra machines")
> > > > Cc: <stable@...r.kernel.org> # 6.1.x
> > > > Cc: <linux-efi@...r.kernel.org>
> > > > Cc: Alexandru Elisei <alexandru.elisei@...il.com>
> > > > Cc: Justin He <Justin.He@....com>
> > > > Cc: Huacai Chen <chenhuacai@...nel.org>
> > > > Cc: "Jason A. Donenfeld" <Jason@...c4.com>
> > > > Cc: Ard Biesheuvel <ardb@...nel.org>
> > > > Signed-off-by: Darren Hart <darren@...amperecomputing.com>
> > > Tested-by: justin.he@....com
> > > > ---
> > > > V1 -> V2: include eMAG
> > > >
> > > >  drivers/firmware/efi/libstub/arm64.c | 9 ++++++---
> > > >  1 file changed, 6 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/drivers/firmware/efi/libstub/arm64.c
> > > > b/drivers/firmware/efi/libstub/arm64.c
> > > > index ff2d18c42ee7..4501652e11ab 100644
> > > > --- a/drivers/firmware/efi/libstub/arm64.c
> > > > +++ b/drivers/firmware/efi/libstub/arm64.c
> > > > @@ -19,10 +19,13 @@ static bool system_needs_vamap(void)
> > > >       const u8 *type1_family = efi_get_smbios_string(1, family);
> > > >
> > > >       /*
> > > > -      * Ampere Altra machines crash in SetTime() if
> SetVirtualAddressMap()
> > > > -      * has not been called prior.
> > > > +      * Ampere eMAG, Altra, and Altra Max machines crash in SetTime()
> if
> > > > +      * SetVirtualAddressMap() has not been called prior.
> > > >        */
> > > > -     if (!type1_family || strcmp(type1_family, "Altra"))
> > > > +     if (!type1_family || (
> > > > +         strcmp(type1_family, "eMAG") &&
> > > > +         strcmp(type1_family, "Altra") &&
> > > > +         strcmp(type1_family, "Altra Max")))
> > > In terms of resolving the boot hang issue, it looks good to me. And
> > > I've verified the "eMAG" part check.
> > > So please feel free to add:
> > > Tested-by: Justin He <justin.he@....com>
> > >
> >
> > Thanks. I've queued this up now.
> >
> > > But I have some other concerns:
> > > 1. On an Altra server, the type1_family returns "Server". I don't
> > > know whether it is a smbios or server firmware bug.
> >
> > This is not really a bug. OEMs are free to put whatever they want into
> > those fields, although that is a great example of a sloppy vendor that
> > just puts random junk in there.
> >
> 
> We could use the type1 "product name" and have a unique identifier, but that
> doesn't scale well either. Ampere partners with many OEMs, and we should
> expect this to increase in time.
> 
> > We could plumb in the type 4 smbios record too, and check the version
> > for *Altra* - however, it would be nice to get an idea of how many
> > more we will end up needing to handle here.
> 
> If we don't get this fixed in firmware, I think we have two kernel side
> maintainable options:
> 
> 1) Depend on the type4 string for the SoCs with impacted EDK2 firmware. This
> is suboptimal as OEMs should be able to update the firmware they ship and
> control how the kernel interacts with their platform. This effectively removes
> that option in order to avoid the individual listing of "product name".
> 
Whether could we introduce a system_force_vamap or similar one to force the 
system_needs_vamap() to return true. I think kernel should allow those
buggy firmware to boot instead of hanging. And the forcible boot parameter is
at least better than the complicated workaround patches.

What do you think of it?

--
Cheers,
Justin (Jia He)

> 2) Revert the earlier commit changing the default to not calling
> SetVirtualAddressMap(). Obviously undesirable for the reasons that patch went
> in, and it affects all arm64 platforms. The only argument here is it used to
> work and now it doesn't.
> 
> > Also, is anyone looking to get this fixed? There is Altra code in the
> > public EDK2 repo, but it is very hard to get someone to care about
> > these things, and fix their firmware.
> 
> Yes, this is a conversation I'm having internally with the firmware teams, and
> the preferred approach provided it can be effectively rolled out to eventually
> capture all Altra* and future platforms.
> 

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