KVM: PPC: Book3S PR: Use 64k host pages where possible

Currently, PR KVM uses 4k pages for the host-side mappings of guest
memory, regardless of the host page size.  When the host page size is
64kB, we might as well use 64k host page mappings for guest mappings
of 64kB and larger pages and for guest real-mode mappings.  However,
the magic page has to remain a 4k page.

To implement this, we first add another flag bit to the guest VSID
values we use, to indicate that this segment is one where host pages
should be mapped using 64k pages.  For segments with this bit set
we set the bits in the shadow SLB entry to indicate a 64k base page
size.  When faulting in host HPTEs for this segment, we make them
64k HPTEs instead of 4k.  We record the pagesize in struct hpte_cache
for use when invalidating the HPTE.

For now we restrict the segment containing the magic page (if any) to
4k pages.  It should be possible to lift this restriction in future
by ensuring that the magic 4k page is appropriately positioned within
a host 64k page.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 4 insertions, 2 deletions

diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
index 1d4a1202e2d5..6bf20b4a2841 100644
--- a/arch/powerpc/include/asm/kvm_book3s.h
+++ b/arch/powerpc/include/asm/kvm_book3s.h
@@ -66,6 +66,7 @@ struct hpte_cache {
 	u64 pfn;
 	ulong slot;
 	struct kvmppc_pte pte;
+	int pagesize;
 };
 
 struct kvmppc_vcpu_book3s {
@@ -113,8 +114,9 @@ struct kvmppc_vcpu_book3s {
 #define CONTEXT_GUEST		1
 #define CONTEXT_GUEST_END	2
 
-#define VSID_REAL	0x0fffffffffc00000ULL
-#define VSID_BAT	0x0fffffffffb00000ULL
+#define VSID_REAL	0x07ffffffffc00000ULL
+#define VSID_BAT	0x07ffffffffb00000ULL
+#define VSID_64K	0x0800000000000000ULL
 #define VSID_1T		0x1000000000000000ULL
 #define VSID_REAL_DR	0x2000000000000000ULL
 #define VSID_REAL_IR	0x4000000000000000ULL