s390/mm: support EDAT1 for gmap shadows

If the guest is enabled for EDAT1, we can easily create shadows for
guest2 -> guest3 provided tables that make use of EDAT1.

If guest2 references a 1MB page, this memory looks consecutive for guest2,
but it might not be so for us. Therefore we have to create fake page tables.

We can easily add that to our existing infrastructure. The invalidation
mechanism will make sure that fake page tables are removed when the parent
table (sgt table entry) is changed.

As EDAT1 also introduced protection on all page table levels, we have to
also shadow these correctly.

We don't have to care about:
- ACCF-Validity Control in STE
- Access-Control Bits in STE
- Fetch-Protection Bit in STE
- Common-Segment Bit in STE

As all bits might be dropped and there is no guaranteed that they are
active ("unpredictable whether the CPU uses these bits", "may be used").
Without using EDAT1 in the shadow ourselfes (STE-format control == 0),
simply shadowing these bits would not be enough. They would be ignored.

Please note that we are using the "fake" flag to make this look consistent
with further changes (EDAT2, real-space designation support) and don't let
the shadow functions handle fc=1 stes.

In the future, with huge pages in the host, gmap_shadow_pgt() could simply
try to map a huge host page if "fake" is set to one and indicate via return
value that no lower fake tables / shadow ptes are required.

Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h
index 2ab397c8ca09..c8ba5a197b1d 100644
--- a/arch/s390/include/asm/gmap.h
+++ b/arch/s390/include/asm/gmap.h
@@ -112,9 +112,10 @@ struct gmap *gmap_shadow(struct gmap *parent, unsigned long asce,
 int gmap_shadow_r2t(struct gmap *sg, unsigned long saddr, unsigned long r2t);
 int gmap_shadow_r3t(struct gmap *sg, unsigned long saddr, unsigned long r3t);
 int gmap_shadow_sgt(struct gmap *sg, unsigned long saddr, unsigned long sgt);
-int gmap_shadow_pgt(struct gmap *sg, unsigned long saddr, unsigned long pgt);
+int gmap_shadow_pgt(struct gmap *sg, unsigned long saddr, unsigned long pgt,
+		    int fake);
 int gmap_shadow_pgt_lookup(struct gmap *sg, unsigned long saddr,
-			   unsigned long *pgt, int *dat_protection);
+			   unsigned long *pgt, int *dat_protection, int *fake);
 int gmap_shadow_page(struct gmap *sg, unsigned long saddr, pte_t pte);
 
 void gmap_register_pte_notifier(struct gmap_notifier *);