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

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Date:	Thu, 5 Dec 2013 21:52:50 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Toshi Kani <toshi.kani@...com>, Dave Young <dyoung@...hat.com>
Cc:	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 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.

Thanks.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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