[CentOS-virt] Garbled screen after RAM Scrub on boot

Tue Feb 23 13:40:41 UTC 2016
Francis Greaves <francis at choughs.net>

Dear George, 
Thanks for the input and ideas. 
Unfortunately bootscrub=false dos not work, not does setting nothing for vga, still get the 'Little white squares'! 
I am asking the xen-users as you suggest 
Regards, Francis 

From: "George Dunlap" <dunlapg at umich.edu> 
To: "Francis Greaves" <francis at choughs.net>, "centos-virt" <centos-virt at centos.org> 
Sent: Tuesday, 23 February, 2016 09:31:40 
Subject: Re: [CentOS-virt] Garbled screen after RAM Scrub on boot 

On Mon, Feb 22, 2016 at 4:18 PM, Francis Greaves <francis at choughs.net> wrote: 
> Dear All 
> I am using Centos 7 with Xen 4.6 on a Dell Poweredge T430 
> 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. 
> My /etc/default/grub is 
> GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)" 
> 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_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 
> What am I doing wrong? 


Thanks for reporting this. I'd suggest re-posting your question on 
xen-users -- there are a lot more eyeballs watching that list than 
this one, and it's easier to "escalate" the issue to the development 
list from there. 

My first instinct is wondering whether grub setting the graphics mode 
is part of the problem. Have you tried having grub just take the bios 
text mode that was given it, rather than changing it? 

(Obviously ideally Xen would work whatever the graphics mode is, but 
most developers are accessing test boxes over serial in a colo, so 
it's not the kind of thing they're prone to notice.) 

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