Re: [Xen-devel] [PATCH v4 8/8] libxl, hvmloader: Don't relocate memory for MMIO hole

["Hao, Xudong" <xudong.hao@xxxxxxxxx>]

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxx
> [mailto:xen-devel-bounces@xxxxxxxxxxxxx] On Behalf Of George Dunlap
> Sent: Friday, June 21, 2013 6:47 PM
> To: xen-devel@xxxxxxxxxxxxx
> Cc: Keir Fraser; Ian Campbell; Hanweidong; George Dunlap; Stefano Stabellini;
> Ian Jackson
> Subject: [Xen-devel] [PATCH v4 8/8] libxl, hvmloader: Don't relocate memory 
> for
> MMIO hole
> 
> At the moment, qemu-xen can't handle memory being relocated by
> hvmloader.  This may happen if a device with a large enough memory
> region is passed through to the guest.  At the moment, if this
> happens, then at some point in the future qemu will crash and the
> domain will hang.  (qemu-traditional is fine.)
> 
> It's too late in the release to do a proper fix, so we try to do
> damage control.
> 
> hvmloader already has mechanisms to relocate memory to 64-bit space if
> it can't make a big enough MMIO hole.  By default this is 2GiB; if we
> just refuse to make the hole bigger if it will overlap with guest
> memory, then the relocation will happen by default.
> 

For qemu-xen use case, hvmloader start MMIO hole at 0xf0000000. However, 
qemu-xen initialize ram region to 0xf0000000(HVM_BELOW_4G_RAM_END) below 4G, 
and pci hole starting from 0xe0000000, is it overlap?

-thanks
Xudong

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