RE: [Xen-devel] [PATCH] Included reserved memory regions in dom0 iommu mappings

[Ross Philipson <Ross.Philipson@xxxxxxxxxx>]

There are some regions that I think would really need to be excluded that are 
related to TXT and tboot too though. The current tboot code puts these in the 
e820 as unusable as apposed to reserved. What if we mapped in all 4GB with the 
exception of unusable ranges and where xen is?

Thanks
Ross

-----Original Message-----
From: Keir Fraser 
Sent: Thursday, February 26, 2009 10:30 AM
To: Cui, Dexuan; Ross Philipson; xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] [PATCH] Included reserved memory regions in dom0 iommu 
mappings

I'm not keen on Ross's patch anyway. I think if you have such a broken
system, the cmdline option should simply identity-map everything below 4GB,
unconditionally. Easy.

 -- Keir

On 26/02/2009 09:20, "Cui, Dexuan" <dexuan.cui@xxxxxxxxx> wrote:

> The patch is useful when BIOS doesn’t report RMRR correctly; however the patch
> may not help in some situations.
> E.g., to work around a buggy BIOS, we may have to map such an E820 entry
> (XEN)  00000000cff0b000 - 00000000d0000000 (reserved).
> But if we use a xen parameter "mem=512m", or, if the host only has 512m
> memory, the variable 'max_page" is 512m/PAGE_SIZE, so even with the patch, the
> E820 entry would not be mapped, and Xen would still hang.
> 
> -- Dexuan
> 
> ________________________________________
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Ross Philipson
> Sent: 2009年2月24日 4:01
> To: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-devel] [PATCH] Included reserved memory regions in dom0 iommu
> mappings
> 
> This adds a boolean boot parameter to xen to allow reserved memory
> regions to be added to the iommu mappings for dom0. The parameter
> is "iommu_include_reserved" and is off by default. A warning is
> also traced when incorrect RMRR to system memory map values are
> detected. This is being added to address some incorrect BIOS's that
> do not report correctly the requied reserved memory ranges in
> the RMRRs. When this occurs it currently can cause early boot hangs
> and crashes.
> 
> Signed-off-by: Ross Philipson <ross.philipson@xxxxxxxxxx>
> 
> Based on changeset 19238
> 
> Thanks
> Ross
> 
> 
> Ross Philipson
> Senior Software Engineer
> Citrix Systems, Inc
> 14 Crosby Drive
> Bedford, MA 01730
> 781-301-7949
> ross.philipson@xxxxxxxxxx
> 



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