[Xen-devel] [PATCH v2] x86/ept: pass correct level to p2m_entry_modify

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

EPT differs from NPT and shadow when translating page orders to levels
in the physmap page tables. EPT page tables level for order 0 pages is
0, while NPT and shadow instead use 1, ie: EPT page tables levels
starts at 0 while NPT and shadow starts at 1.

Fix the p2m_entry_modify call in atomic_write_ept_entry to always add
one to the level, in order to match NPT and shadow usage.

While there also add a check to ensure p2m_entry_modify is never
called with level == 0. That should allow to catch future errors
related to the level parameter.

Fixes: c7a4c088ad1c ('x86/mm: split p2m ioreq server pages special handling 
into helper')
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Cc: Jun Nakajima <jun.nakajima@xxxxxxxxx>
Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Wei Liu <wl@xxxxxxx>
---
Changes since v1:
 - Check level is != 0 in p2m_entry_modify.
 - Expand digits of hash id.
---
 xen/arch/x86/mm/p2m-ept.c | 2 +-
 xen/include/asm-x86/p2m.h | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index e3044bee2e..6b8468c793 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -51,7 +51,7 @@ static int atomic_write_ept_entry(struct p2m_domain *p2m,
                                   int level)
 {
     int rc = p2m_entry_modify(p2m, new.sa_p2mt, entryptr->sa_p2mt,
-                              _mfn(new.mfn), _mfn(entryptr->mfn), level);
+                              _mfn(new.mfn), _mfn(entryptr->mfn), level + 1);
 
     if ( rc )
         return rc;
diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
index 09ef7e02fd..aff34e3adf 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -946,6 +946,7 @@ static inline int p2m_entry_modify(struct p2m_domain *p2m, 
p2m_type_t nt,
                                    p2m_type_t ot, mfn_t nfn, mfn_t ofn,
                                    unsigned int level)
 {
+    BUG_ON(!level);
     BUG_ON(level > 1 && (nt == p2m_ioreq_server || nt == p2m_map_foreign));
 
     if ( level != 1 || (nt == ot && mfn_eq(nfn, ofn)) )
-- 
2.20.1 (Apple Git-117)


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