tree 518b4ff17a8e1e62b747ce1912c08b62883d2855
parent df9b856c454e331bc394c80903fcdea19cae2a33
author Hollis Blanchard <hollisb@us.ibm.com> 1226350656 -0600
committer Avi Kivity <avi@redhat.com> 1230735146 +0200

KVM: ppc: fix userspace mapping invalidation on context switch

We used to defer invalidating userspace TLB entries until jumping out of the
kernel. This was causing MMU weirdness most easily triggered by using a pipe in
the guest, e.g. "dmesg | tail". I believe the problem was that after the guest
kernel changed the PID (part of context switch), the old process's mappings
were still present, and so copy_to_user() on the "return to new process" path
ended up using stale mappings.

Testing with large pages (64K) exposed the problem, probably because with 4K
pages, pressure on the TLB faulted all process A's mappings out before the
guest kernel could insert any for process B.

Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>