Re: [Xen-users] Garbled screen after RAM Scrub on boot

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 07/03/16 14:33, George Dunlap wrote:
> Jan / Konrad,
>
> Have you guys ever seen something like this before?  Any ideas how to proceed?
>
> Thanks
>  -George

Sounds like the scrub is writing zeroes over the graphics framebuffer. 
This probably means that the firmware is using a region for the
framebuffer which isn't marked as reserved in the E820 region.

~Andrew

>
> On Tue, Feb 23, 2016 at 1:37 PM, Francis Greaves <francis@choughs.net> wrote:
>> Dear All
>> I am using Centos 7 with Xen 4.6 on a Dell Poweredge T430 with (from lspci)
>> Matrox Electronics Systems Ltd. G200eR2 (rev 01) VGA
>>
>> When the machine boots, after the 'Scrubbing Free RAM' message, I get a
>> screen filled with little white squares until the login prompt, so I cannot
>> see what is happening as the machine boots. Also there is nothing on the
>> screen when I reboot or shutdown.
>>
>> My /etc/default/grub is
>>
>> GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
>> GRUB_DEFAULT=saved
>> GRUB_DISABLE_SUBMENU=true
>> GRUB_CMDLINE_LINUX="crashkernel=auto rhgb intremap=no_x2apic_optout"
>> GRUB_CMDLINE_XEN_DEFAULT="dom0_mem=13312M,max:14336M dom0_max_vcpus=6
>> dom0_vcpus_pin"
>> GRUB_GFXMODE=1024x768
>> GRUB_GFXPAYLOAD_LINUX=keep
>> GRUB_CMDLINE_LINUX_XEN_REPLACE_DEFAULT="console=hvc0 earlyprintk=xen
>> nomodeset"
>>
>> I have tried setting (for a 1024x768 resolution) vga=792 in the
>> GRUB_CMDLINE_LINUX and commenting out GRUB_GFXMODE and
>> GRUB_GFXPAYLOAD_LINUX, but this makes no difference.
>> I have also tried with no settings for vga at all, and with and without
>> 'rhgb'
>> I have even tried bootscrub=false as suggested by the CentOS-virt mailing
>> list, but that does not work either. They suggested I asked you folk.
>>
>> What am I doing wrong?
>>
>> Regards
>> Francis
>>
>>
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