Re: [Xen-devel] [PATCH] iomem: Prevent Dom0 pci bus from allocating RAM as I/O space

[Fengzhe Zhang <fengzhe.zhang@xxxxxxxxx>]

On 2011/2/16 23:47, Konrad Rzeszutek Wilk wrote:
> On Wed, Feb 16, 2011 at 10:20:21AM -0500, Konrad Rzeszutek Wilk wrote:
> > On Wed, Feb 16, 2011 at 10:06:38AM -0500, Konrad Rzeszutek Wilk wrote:
> > > On Wed, Feb 16, 2011 at 10:26:20PM +0800, Zhang, Fengzhe wrote:
> > > > iomem: Prevent Dom0 pci bus from allocating RAM as I/O space
> > > Is there a bug # associated with this? Is this associated with the intel-agp
> > > driver trying to ioremap the scratch page and bombing out?
> Also did you try to revert 0b56d9994ebe34df77fa156d2068ad93b7877b44 and see
> how that works? Here is the revert attached
I tried this patch and it can indeed avoid system crash.

However, I still doubt if the igb device is working correctly. The 
sequence that igb driver do ioremap is like this:
1. igb calls function pci_ubs_alloc_resource to get some non-RAM pages.
2. igb sets the phys_addr of the pages in some BAR.
3. igb ioremaps these pages.

After patching, it looks like ioremap gets some mfn allocated by Xen. 
But what set in BAR is still phys_addr. If igb device tries to access 
the pages directly, would Xen be able to intercept and translate it? And 
also, how the contiguity of mfns be guaranteed?
-Fengzhe

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