linux-kernel - Re: [PATCH v1 2/2] firmware: dmi_scan: Pass dmi_entry

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Message-ID: <20161217105721.GB6922@dhcp-128-65.nay.redhat.com>
Date:   Sat, 17 Dec 2016 18:57:21 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Jean Delvare <jdelvare@...e.de>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        kexec@...ts.infradead.org,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
        matt@...eblueprint.co.uk, ard.biesheuvel@...aro.org
Subject: Re: [PATCH v1 2/2] firmware: dmi_scan: Pass dmi_entry_point to
 kexec'ed kernel

Ccing efi people.

On 12/16/16 at 02:33pm, Jean Delvare wrote:
> On Fri, 16 Dec 2016 14:18:58 +0200, Andy Shevchenko wrote:
> > On Fri, 2016-12-16 at 10:32 +0800, Dave Young wrote:
> > > On 12/15/16 at 12:28pm, Jean Delvare wrote:
> > > > I am no kexec expert but this confuses me. Shouldn't the second
> > > > kernel have access to the EFI systab as the first kernel does? It
> > > > includes many more pointers than just ACPI and DMI tables, and it
> > > > would seem inconvenient to have to pass all these addresses
> > > > individually explicitly.
> > > 
> > > Yes, in modern linux kernel, kexec has the support for EFI, I think it
> > > should work naturally at least in x86_64.
> > 
> > Thanks for this good news!
> > 
> > Unfortunately Intel Galileo is 32-bit platform.
> 
> If it was done for X86_64 then maybe it can be generalized to X86?

For X86_64, we have a new way for efi runtime memmory mapping, in i386
code it still use old ioremap way. It is impossible to use same way as
the X86_64 since the virtual address space is limited.

But maybe for 32bit, kexec kernel can run in physical mode, but I'm not
sure, I would suggest Andy to do a test first with efi=noruntime for
kexec 2nd kernel.

Thanks
Dave

> 
> -- 
> Jean Delvare
> SUSE L3 Support