Re: [Xen-devel] Xen, MCFG acpi table and E820 address map

[Santosh Jodh <Santosh.Jodh@xxxxxxxxxx>]

-----Original Message-----
From: Gordan Bobic [mailto:gordan@xxxxxxxxxx] 
Sent: Wednesday, September 04, 2013 9:24 AM
To: Santosh Jodh
Cc: Konrad Rzeszutek Wilk; Jan Beulich; xen-devel; Boris Ostrovsky; David Vrabel
Subject: Re: [Xen-devel] Xen, MCFG acpi table and E820 address map

 On Wed, 4 Sep 2013 16:14:55 +0000, Santosh Jodh  <Santosh.Jodh@xxxxxxxxxx> 
wrote:
> -----Original Message-----
> From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx]
> Sent: Wednesday, September 04, 2013 8:01 AM
> To: Jan Beulich
> Cc: Santosh Jodh; David Vrabel; xen-devel; Boris Ostrovsky
> Subject: Re: [Xen-devel] Xen, MCFG acpi table and E820 address map
>
> On Wed, Sep 04, 2013 at 10:16:26AM +0100, Jan Beulich wrote:
>> >>> On 04.09.13 at 03:13, Santosh Jodh <Santosh.Jodh@xxxxxxxxxx>
>> wrote:
>> > Xen will use information from MCFG acpi table to access PCIe 
>> > extended configuration space. However, Xen validates MCFG table by 
>> > making sure that the addresses specified in the MCFG table is 
>> > correctly marked as reserved in the E820 address map. If it is
>> not,
>> > the MCFG table is ignored - thereby preventing Xen from accessing
>> PCIe extended configuration space.
>> >
>> > I recently came across a workstation class system that supports 
>> > VT-d. This system BIOS has a valid MCFG table. The BIOS does NOT 
>> > report the MCFG addresses as reserved in the E820 address map.
>> > However, the addresses ARE claimed as reserved via the ACPI 
>> > motherboard resource devnode (PNP0C01) mechanism.
>
> Could you tell me what machine this is? It would be good to know to 
> develop a patch against it.
> [Santosh Jodh] Unfortunately, this is a new platform I cannot disclose 
> much about.

 If this is pre-release/experimental hardware, isn't the  right thing to do to 
talk to the manufacturer and get them  to fix the BIOS so it exposes the 
correct e820 map in the  first place?
[Santosh Jodh] yes - BIOS fix is in progress. My original query was - is this 
an exception? If it is a trend, then Xen should handle this better.

 Gordan
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