Re: [Xen-devel] debian stretch dom0 + xen 4.9 fails to boot

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 06/09/2017 09:05 AM, Jan Beulich wrote:
>>>> On 09.06.17 at 14:19, <Paul.Durrant@xxxxxxxxxx> wrote:
>> ..., but all this has 
>> got me wondering why Xen bothers to read the MBR, or the EDD info for that 
>> matter? EDD or MBR signatures are returned by the XENPF_firmware_info 
>> hypercall, and Linux does seem to have code called early on in 
>> xen_start_kernel() that does make such hypercalls, but it also appears to be 
>> able to boot happily if I put edd=off on my Xen command line, so is this 
>> code 
>> really necessary?
> Well, that's a question to the Linux folks. I would guess there's
> management code around wanting that info, but I'm not sure. Us
> doing this is simply because of Linux wanting it and having no
> other way to get at least some of this information (it could surely
> read the MBRs, but it wouldn't be able to associate them with
> BIOS drive numbers used for the other EDD information obtained).

Not sure what it is for. Perhaps there are some tools that poke into sysfs?


commit 96f28bc66adb1414cfc9405ff80cfffdc44edd84
Author: David Vrabel <david.vrabel@xxxxxxxxxx>
Date:   Wed Apr 3 17:31:50 2013 +0100

    x86/xen: populate boot_params with EDD data
   
    During early setup of a dom0 kernel, populate boot_params with the
    Enhanced Disk Drive (EDD) and MBR signature data.  This makes
    information on the BIOS boot device available in /sys/firmware/edd/.
   
    Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>


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