KVM: PPC: Implement MMU notifiers for Book3S HV guests

This adds the infrastructure to enable us to page out pages underneath
a Book3S HV guest, on processors that support virtualized partition
memory, that is, POWER7.  Instead of pinning all the guest's pages,
we now look in the host userspace Linux page tables to find the
mapping for a given guest page.  Then, if the userspace Linux PTE
gets invalidated, kvm_unmap_hva() gets called for that address, and
we replace all the guest HPTEs that refer to that page with absent
HPTEs, i.e. ones with the valid bit clear and the HPTE_V_ABSENT bit
set, which will cause an HDSI when the guest tries to access them.
Finally, the page fault handler is extended to reinstantiate the
guest HPTE when the guest tries to access a page which has been paged
out.

Since we can't intercept the guest DSI and ISI interrupts on PPC970,
we still have to pin all the guest pages on PPC970.  We have a new flag,
kvm->arch.using_mmu_notifiers, that indicates whether we can page
guest pages out.  If it is not set, the MMU notifier callbacks do
nothing and everything operates as before.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 16efb31..35c9309 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -495,6 +495,9 @@
 #define SPRN_SPRG7	0x117	/* Special Purpose Register General 7 */
 #define SPRN_SRR0	0x01A	/* Save/Restore Register 0 */
 #define SPRN_SRR1	0x01B	/* Save/Restore Register 1 */
+#define   SRR1_ISI_NOPT		0x40000000 /* ISI: Not found in hash */
+#define   SRR1_ISI_N_OR_G	0x10000000 /* ISI: Access is no-exec or G */
+#define   SRR1_ISI_PROT		0x08000000 /* ISI: Other protection fault */
 #define   SRR1_WAKEMASK		0x00380000 /* reason for wakeup */
 #define   SRR1_WAKESYSERR	0x00300000 /* System error */
 #define   SRR1_WAKEEE		0x00200000 /* External interrupt */