linux-kernel - Re: [PATCH v4 07/12] efi: passing kexec necessary efi data via setup

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Date:	Fri, 6 Dec 2013 09:31:44 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Toshi Kani <toshi.kani@...com>, linux-kernel@...r.kernel.org,
	linux-efi@...r.kernel.org, x86@...nel.org, mjg59@...f.ucam.org,
	hpa@...or.com, James.Bottomley@...senPartnership.com,
	vgoyal@...hat.com, ebiederm@...ssion.com, horms@...ge.net.au,
	kexec@...ts.infradead.org, greg@...ah.com, matt@...sole-pimps.org
Subject: Re: [PATCH v4 07/12] efi: passing kexec necessary efi data via
 setup_data

On 12/05/13 at 09:52pm, Borislav Petkov wrote:
> On Thu, Dec 05, 2013 at 08:56:02AM -0700, Toshi Kani wrote:
> > The smbios in efi_setup_data is necessary for kexec to pass the physical
> > address of the SMBIOS table from the 1st kernel to the 2nd kernel.
> > 
> > The kernel boot sequence proceeds in the following order.  Step 2
> > requires efi.smbios to be the physical address.  However, Dave found
> > that EFI system table has a virtual address of SMBIOS in step 1.  Hence,
> > he sets it back to the physical address with the smbios in
> > efi_setup_data.  (When it is still the physical address, it simply sets
> > the same value.)
> > 
> > 1. efi_init() - Set efi.smbios from EFI system table
> > 2. dmi_scan_machine() - Temporary map efi.smbios to access SMBIOS table
> > 3. efi_enter_virtual_mode() - Map EFI ranges
> 
> Thanks Toshi, it is all clear now.
> 
> @Dave: you might want to put Toshi's explanation in the commit message
> of your patch so that we know *why* the change is needed.

Ok, will do.

Thanks
Dave
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