On 06/04/2018 06:39 PM, Andrew Cooper wrote:

On 04/06/18 14:59, Andrew Cooper wrote:

So this started as a small fix for the vmentry failure (penultimate patch),
and has snowballed...

I'm fairly confident that everything involving DEBUGCTL.BTF is broken, and
there are definitely bugs with configuring DEBUGCTL.RTM (which really isn't
helped by the fact that the GCC TSX intrinsics render the resulting code
un-debuggable.)  I'll defer fixing these swamps for now.

The first 4 patches probably want backporting to the stable trees, so I've
taken care to move them ahead of patch 6 for backport reasons.  While all
fixes would ideally be backported, I can't find a way of fixing %dr6 merging
(as it needs to be done precicely once) without a behavioural change in the
monitor subsystem.

Patch 8 probably breaks introspection, so can't be taken at this point.  See
that patch for discussion of the problem and my best guess at a solution.

As spotted by Razvan, I forgot to mention that this series is built on
top of "x86/vmx: Fix handing of MSR_DEBUGCTL on VMExit".  It can be
found in git form here:

http://xenbits.xen.org/gitweb/?p=people/andrewcoop/xen.git;a=shortlog;h=refs/heads/debug-fixes-v1

FWIW, you're exactly right about the recursive injection vm_events. I've
tested this with xen-access and the test-hvm64-swint-emulation XTF test:

1. xl create xl create -p ./test-hvm64-swint-emulation.cfg
2. xen-access <DOMID> breakpoint
3. xl unpause <DOMID>

The test domain will not be able to finish until xen-access is stopped
(with ^C).

So this does indeed break introspection the way it is now implemented.