tree b059ff799f8cec85a315874acdf49c693d7e2681
parent 8296963e6e8c656c4d91dfa7245e49672aa9675e
author James Hogan <james.hogan@imgtec.com> 1467975210 +0100
committer Paolo Bonzini <pbonzini@redhat.com> 1470069747 +0200

MIPS: KVM: Reset CP0_PageMask during host TLB flush

KVM sometimes flushes host TLB entries, reading each one to check if it
corresponds to a guest KSeg0 address. In the absence of EntryHi.EHInv
bits to invalidate the whole entry, the entries will be set to unique
virtual addresses in KSeg0 (which is not TLB mapped), spaced 2*PAGE_SIZE
apart.

The TLB read however will clobber the CP0_PageMask register with
whatever page size that TLB entry had, and that same page size will be
written back into the TLB entry along with the unique address.

This would cause breakage when transparent huge pages are enabled on
64-bit host kernels, since huge page entries will overlap other nearby
entries when separated by only 2*PAGE_SIZE, causing a machine check
exception.

Fix this by restoring the old CP0_PageMask value (which should be set to
the normal page size) after reading the TLB entry if we're going to go
ahead and invalidate it.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>