Re: [Xen-devel] RE: [RFC][PATCH][VTD] EPT/VT-d page table sharing

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Sat, 2010-12-11 at 02:01 +0000, Kay, Allen M wrote:
> Hi Tim,
> 
> Thanks for your feedback.  In attached updated patch, I have:
> 
>    1) moved setting of iommu_hap_pt_share flag to init_vtd_hw(). This 
> function initialized other vt-d specific features.  Let me know if you know 
> of a better place.
>    2) rename avail2 field to sa_p2mt.
> 
> Let me know if you have any additional comments.

Hi Allen,

This change appears to be responsible for the recent failures to boot
xen-unstable on Intel hardware, which is stopping the regression test
runs.

The symptom is a hang just before the hypervisor scrubs the pages. e.g.
http://www.chiark.greenend.org.uk/~xensrcts/logs/3470/test-amd64-i386-rhel6hvm-intel/
was successful while
http://www.chiark.greenend.org.uk/~xensrcts/logs/3863/test-amd64-i386-rhel6hvm-intel/
was not.

Booting with "sharept=0" resolves the boot failure.

It's been quite a long time (~2 weeks) since we last had a test case
(not all down to this issue) so unless you have a quick fix I propose
the temporary workaround below.

Thanks,
Ian.

EPT/VT-d: disable page sharing by default.

Currently sharing these page tables causes a hang on boot on some
hardware. Disable by default until this is resolved.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

diff -r ff1b80ccecd9 xen/drivers/passthrough/vtd/iommu.c
--- a/xen/drivers/passthrough/vtd/iommu.c       Fri Dec 17 16:12:37 2010 +0000
+++ b/xen/drivers/passthrough/vtd/iommu.c       Tue Dec 21 16:24:34 2010 +0000
@@ -45,7 +45,7 @@
 #define nr_ioapics              iosapic_get_nr_iosapics()
 #endif
 
-static int sharept = 1;
+static int sharept = 0;
 boolean_param("sharept", sharept);
 
 int nr_iommus;



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel