[Xen-devel] xen-access performance from DomU

[Bread Cutter <cutter409@xxxxxxxxx>]

Hello all,

I'm having a performance issue with the xen-access API from DomU.

First of all, I've changed xen/include/xsm/dummy.h so that all
permissions are allowed. This is temporary and for testing, simply so
that I could run xen-access from DomU. I've also changed
tools/tests/xen-access/xen-access.c (patch attached) so that I monitor
cr3 writes. This was just something that happens consistently enough
for comparing performance. The actual value of cr3 isn't important for
my testing.

When I run xenaccess in Dom0, the target HVM domain runs pretty
smoothly. I can launch programs and Windows feels pretty responsive.

However, when I run the same tool from a PV-DomU, the target domain
becomes extremely sluggish. Launching a web browser takes a long time,
for example, and it's essentially unusable.

Can anyone offer any insight, and/or a remedy?

Thank you!

Attachment: xen-access_cr3.patch
Description: Text Data

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