Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit

From: Boris Ostrovsky
Date: Mon Nov 16 2015 - 15:49:13 EST

On 11/16/2015 03:22 PM, Borislav Petkov wrote:
On Mon, Nov 16, 2015 at 12:11:11PM -0800, Andy Lutomirski wrote:

Are there really multiple feature bits for this stuff? I'd like to
imagine that the entry code is all either Xen PV or native/PVH/PVHVM
-- i.e. I assumed that PVH works like native for all entries.

Almost. For PVH we will have a small stub to set up bootparams and such but then we jump to startup_{32|64} code.

I just reacted to Boris' statement:

"We don't currently have a Xen-specific CPU feature. We could, in
principle, add it but we can't replace all of current paravirt patching
with a single feature since PVH guests use a subset of existing pv ops
(and in the future it may become even more fine-grained)."

Actually, nevermind this --- I was thinking about APIC ops and they are not pv ops.

Note though that there are other users of pv ops --- lguest and looks like KVM (for one op) use them too.

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