KVM: PPC: Deflect page write faults properly in kvmppc_st

When we have a page that we're not allowed to write to, xlate() will already
tell us -EPERM on lookup of that page. With the code as is we change it into
a "page missing" error which a guest may get confused about. Instead, just
tell the caller about the -EPERM directly.

This fixes Mac OS X guests when run with DCBZ32 emulation.

Signed-off-by: Alexander Graf <agraf@suse.de>
KVM: PPC: Book3S: Stop PTE lookup on write errors

When a page lookup failed because we're not allowed to write to the page, we
should not overwrite that value with another lookup on the second PTEG which
will return "page not found". Instead, we should just tell the caller that we
had a permission problem.

This fixes Mac OS X guests looping endlessly in page lookup code for me.

Signed-off-by: Alexander Graf <agraf@suse.de>