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Re: [Xen-devel] [Patch] Make memory hole for PCI Express bigger and prevent roll-over

  • To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>
  • From: "David Stone" <unclestoner@xxxxxxxxx>
  • Date: Mon, 21 Jan 2008 08:41:46 -0500
  • Cc: Xen Developers <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Mon, 21 Jan 2008 05:42:11 -0800
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On Jan 18, 2008 4:31 PM, Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> wrote:
> That's a very big hole. We should do this more dynamically.

OK fair enough.  As I said I have some code that dynamically modifies
the DSDT's AML.  I'll try to finish it up and submit it.

But in the meantime, will you take a patch (a subset of the patch I
just submitted) that keeps the hole as it is (starting at 0xF0000000)
but ensures it doesn't roll over to 0x00000000 in the Xen HVM BIOS?

Also should the hole used by the Xen HVM BIOS be limited to
0xF0000000-0xF4FFFFFF rather than 0xF00000000-0xFFFFFFFF?  Because:
  - The current DSDT specifies 0xF0000000-0xF4FFFFFF.
  - My understanding is that various other systems/components use
certain addresses at the top of 32-bit physical address space (like
maybe MSIs?).  So it would be bad to assign those physical addresses
to random PCI devices.
My only hesitation is that 0xF0000000-0xF4FFFFFF = 80Mb is smallish,
especially considering the wasteful algorithm the Xen HVM BIOS
currently uses to assign addresses (it can waste a lot of space).


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