linux-kernel - Re: [PATCH v1 0/2] firmware: dmi_scan: Make it work in kexec'ed kernel

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Message-ID: <YL9hxPdPj0dYMyaD@dhcp-128-65.nay.redhat.com>
Date:   Tue, 8 Jun 2021 20:25:40 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Jean Delvare <jdelvare@...e.com>, linux-kernel@...r.kernel.org,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Javier Tiá <javier.tia@...il.com>,
        kexec@...ts.infradead.org, Eric Biederman <ebiederm@...ssion.com>,
        linux-efi <linux-efi@...r.kernel.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Ard Biesheuvel <ardb@...nel.org>
Subject: Re: [PATCH v1 0/2] firmware: dmi_scan: Make it work in kexec'ed
 kernel

On 06/07/21 at 08:18pm, Andy Shevchenko wrote:
> On Mon, Jun 07, 2021 at 07:22:21PM +0300, Andy Shevchenko wrote:
> > On Sat, Jun 05, 2021 at 03:51:05PM +0800, Dave Young wrote:
> > > On 06/02/21 at 11:53am, Andy Shevchenko wrote:
> > > > On Wed, Jun 02, 2021 at 11:42:14AM +0300, Andy Shevchenko wrote:
> > > > > On Fri, Dec 02, 2016 at 09:54:14PM +0200, Andy Shevchenko wrote:
> > > > > > Until now DMI information is lost when kexec'ing. Fix this in the same way as
> > > > > > it has been done for ACPI RSDP.
> > > > > > 
> > > > > > Series has been tested on Galileo Gen2 where DMI is used by drivers, in
> > > > > > particular the default I2C host speed is choosen based on DMI system
> > > > > > information and now gets it correct.
> > > > > 
> > > > > Still nothing happens for a while and problem still exists.
> > > > > Can we do something about it, please?
> > > 
> > > Seems I totally missed this thread. Old emails lost.
> > 
> > You can always access to it via lore :-)
> > https://lore.kernel.org/linux-efi/20161217105721.GB6922@dhcp-128-65.nay.redhat.com/T/#u

Thanks.  Hmm, this is for 32bit efi.  kexec efi boot support was only
added for 64bit. So if 32bit dmidecode does not work I'm not surprise.

> > 
> > (Okay, it's not full, but contains main parts anyway)
> > 
> > 
> > > The question Ard asked is to confirm if the firmware converted the
> > > SMBIOS3 addr to a virtual address after exit boot service. I do not
> > > remember some easy way to check it due to lost the context of the code.
> > > But you can try to check it via dmesg|grep SMBIOS both in normal boot
> > > and kexeced boot log.  And then compare if those addresses are
> > > identical.
> > > 
> > > If the SMBIOS3 addr in kexec kernel is different then it should have
> > > been modified by firmware. Then we need patch kernel and kexec-tools to
> > > support it.
> > > 
> > > You can try below patch to see if it works:
> > 
> > So, AFAIU I have to apply patch to kexec tools for the fist kernel + userspace
> > and apply kernel patch for the second kernel? Or it's all for the first one?
> > 
> > > apply a kexec-tools patch to kexec-tools if you do not use kexec -s
> > > (kexec_file_load):
> > 
> > Here is how we are using it:
> > https://github.com/andy-shev/buildroot/blob/intel/board/intel/common/netboot/udhcpc-script.sh#L54
> 
> Okay, thanks for the patches. I have applied them to both kernels, so the first
> one and second one are the same and kexec tools have a patch provided in the
> user space of the both kernels (only first one in use though).
> 
> Before applying your patch, I have reverted my hacks (as per this series).
> 
> Result is:
> 
> # uname -a
> Linux buildroot 5.13.0-rc5+ #1 SMP Mon Jun 7 19:49:40 EEST 2021 i586 GNU/Linux
> # dmidecode
> # dmidecode 3.3
> Scanning /dev/mem for entry point.
> # No SMBIOS nor DMI entry point found, sorry.
> 
> I.o.w. it does NOT fix the issue. My patches do (with a hint from user space).

As I said, since it is 32bit efi, so your test results are expected,
also no need to check the kernel log about SMBIOS3 address changed or
not.

> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
> 

Thanks
Dave