From mboxrd@z Thu Jan  1 00:00:00 1970
From: George Dunlap <george.dunlap@eu.citrix.com>
Subject: Re: Limitation in HVM physmap
Date: Fri, 18 Oct 2013 16:06:01 +0100
Message-ID: <52614E59.50103@eu.citrix.com>
References: <20131018142012.GB20185@zion.uk.xensource.com>
	<20131018142824.GA33100@deinos.phlegethon.org>
	<20131018143640.GC20185@zion.uk.xensource.com>
	<20131018144149.GB33100@deinos.phlegethon.org>
	<20131018145611.GD20185@zion.uk.xensource.com>
	<1382108350.6933.3.camel@kazak.uk.xensource.com>
	<20131018150417.GF20185@zion.uk.xensource.com>
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To: Wei Liu <wei.liu2@citrix.com>, Ian Campbell <Ian.Campbell@citrix.com>
Cc: keir@xen.org, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Tim Deegan <tim@xen.org>, Jan Beulich <JBeulich@suse.com>, xen-devel@lists.xen.org
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On 18/10/13 16:04, Wei Liu wrote:
> On Fri, Oct 18, 2013 at 03:59:10PM +0100, Ian Campbell wrote:
> [...]
>>> During OVMF initialization:
>>>
>>> (d28) PciBus: Resource Map for Root Bridge PciRoot(0x0)
>>> (d28) Type =   Io16; Base = 0xC000;     Length = 0x1000;        Alignment = 0xFFF
>>> (d28)  Base = 0xC000;   Length = 0x100; Alignment = 0xFF;       Owner = PCI  [00|04|
>>> (d28)  Base = 0xC100;   Length = 0x100; Alignment = 0xFF;       Owner = PCI  [00|03|
>>> (d28)  Base = 0xC200;   Length = 0x10;  Alignment = 0xF;        Owner = PCI  [00|01|
>>> (d28) Type =  Mem32; Base = 0x80000000; Length = 0x3100000;     Alignment = 0x1FFFFF
>>> (d28)  Base = 0x80000000;       Length = 0x2000000;     Alignment = 0x1FFFFFF;  Owne
>>> (d28) |02|00:10]
>>>
>>> Later when Linux loads EFIFB driver:
>>> [    2.628264] efifb: framebuffer at 0x80000000, mapped to
>>> 0xffffc90000100000, using 1876k, total 1875k
>>> [    2.646827] efifb: mode is 800x600x32, linelength=3200, pages=1
>>> [    2.658833] efifb: scrolling: redraw
>>> [    2.666342] efifb: Truecolor: size=8:8:8:8, shift=24:16:8:0
>>>
>>> 0xf0000000 is mapped by:
>> What hardware is backing the framebuffer at 0x80000000? It doesn't
>> appear to be this cirrus device.
>>
> Looking that the "Resource Map for Root Bridge" 0x8000000 is backed by
> 00:02:00 (trancated above) and 00:02.0 is also owned by Cirrus Logic
> driver...

xentrace -e all should give you a record of all calls to 
set_p2m_entry(), as well as any MMIO / PIO, so you should be able to 
verify the remapping / double mapping happening from the other direction.

  -George