process softirqs while dumping domains

Process softirqs once per domain, and once every 64 vcpus in a guest to avoid
being hit by the NMI watchdog.  Discovered against a VM which had accidentally
been assigned 8192 vcpus.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Dario Faggioli <dario.faggioli@citrix.com>
VMX: values written to MSR_IA32_SYSENTER_E[IS]P should be canonical

A recent KVM change by Nadav Amit <namit@cs.technion.ac.il> helped spot
that we have the same issue as they did.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Tim Deegan <tim@xen.org>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>
x86/HVM: only kill guest when unknown VM exit occurred in guest kernel mode

A recent KVM change by Nadav Amit <namit@cs.technion.ac.il> pointed out
that unconditional VM exits (like VMX'es ones for the INVEPT, INVVPID,
and XSETBV instructions) may result from guest user mode activity (in
the example cases, e.g. prior to a privilege level check being done).
Consequently convert the unconditional domain_crash() to a conditional
one (when guest is in kernel mode) with the alternative of injecting
#UD (when in user mode).

This is meant to be a precaution against in-guest security issues
introduced when any such VM exit becomes possible (on newer hardware)
without the hypervisor immediately being aware of it. There are no such
unhandled VM exits currently (and hence this is not an active security
issue), but old (no longer security maintained) versions exhibit issues
in the cases given as examples above.

Suggested-by: Tim Deegan <tim@xen.org>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>