From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jan Beulich" <JBeulich@suse.com>
Subject: Re: GPU passthrough performance regression in >4GB vms
 due to XSA-60 changes
Date: Thu, 15 May 2014 14:23:41 +0100
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To: Tomasz Wroblewski <tomasz.wroblewski@gmail.com>
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>>> On 15.05.14 at 14:10, <tomasz.wroblewski@gmail.com> wrote:
> Not really sure why it only affects 64bit vms but I've just noticed the 
> pci BARs for the card are being relocated by hvmloader as per some logs:
> 
> (XEN) HVM3: Relocating guest memory for lowmem MMIO space enabled
> (XEN) HVM3: Relocating 0xffff pages from 0e0001000 to 14dc00000 for 
> lowmem MMIO hole
> (XEN) HVM3: Relocating 0x1 pages from 0e0000000 to 15dbff000 for lowmem 
> MMIO hole
> 
> So it might be also related to that.

Indeed it might - what are the (guest) MTRR types for those regions?

Jan