tree 0a4debf31f537b5c7e02f9737f0429f7112c7f60
parent cbd905dac5357a3b9c3ebd0343833bfd88884c2a
author Radim Krcmar <rkrcmar@redhat.com> 1565753857 -0400
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1567758131 +0200

kvm: x86: skip populating logical dest map if apic is not sw enabled

commit b14c876b994f208b6b95c222056e1deb0a45de0e upstream.

recalculate_apic_map does not santize ldr and it's possible that
multiple bits are set. In that case, a previous valid entry
can potentially be overwritten by an invalid one.

This condition is hit when booting a 32 bit, >8 CPU, RHEL6 guest and then
triggering a crash to boot a kdump kernel. This is the sequence of
events:
1. Linux boots in bigsmp mode and enables PhysFlat, however, it still
writes to the LDR which probably will never be used.
2. However, when booting into kdump, the stale LDR values remain as
they are not cleared by the guest and there isn't a apic reset.
3. kdump boots with 1 cpu, and uses Logical Destination Mode but the
logical map has been overwritten and points to an inactive vcpu.

Signed-off-by: Radim Krcmar <rkrcmar@redhat.com>
Signed-off-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>