[Xen-devel] [PATCH] xen/p2m: Remove np2m-specific filter from generic p2m_flush_table

[George Dunlap <george.dunlap@xxxxxxxxxx>]

Commit 71bb7304e7a7a35ea6df4b0cedebc35028e4c159 added flushing of
nested p2m tables whenever the host p2m table changed.  Unfortunately
in the process, it added a filter to the generic p2m_flush_table()
function so that the p2m would only be flushed if it was being used as
a nested p2m.  This meant that the p2m was not being flushed at all
for altp2m callers.

Instead do the nested p2m filtering in p2m_flush_nestedp2m().

NB that this is not a security issue: The only time this codepath is
called is in cases where either nestedp2m or altp2m is enabled, and
neither of them are in security support.

Reported-by: Matt Leinhos <matt@xxxxxxxxxx>
Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxx>
---
I've smoke-tested this with nested virt and it seems to work fine.
Matt / Tamas, could you test this with altp2m and see if it fixes your
issue?


CC: Liang Li <liang.z.li@xxxxxxxxx>
CC: Yang Zhang <yang.z.zhang@xxxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
CC: Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>
CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Jan Beulich <jbeulich@xxxxxxxx>
CC: Matt Leinhos <matt@xxxxxxxxxx>
---
 xen/arch/x86/mm/p2m.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index aa627d8..0849c6e 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -2048,12 +2048,6 @@ p2m_flush_table(struct p2m_domain *p2m)
     ASSERT(page_list_empty(&p2m->pod.super));
     ASSERT(page_list_empty(&p2m->pod.single));
 
-    if ( p2m->np2m_base == P2M_BASE_EADDR )
-    {
-        p2m_unlock(p2m);
-        return;
-    }
-
     /* This is no longer a valid nested p2m for any address space */
     p2m->np2m_base = P2M_BASE_EADDR;
     
@@ -2088,7 +2082,11 @@ p2m_flush_nestedp2m(struct domain *d)
 {
     int i;
     for ( i = 0; i < MAX_NESTEDP2M; i++ )
-        p2m_flush_table(d->arch.nested_p2m[i]);
+    {
+        struct p2m_domain *p2m = d->arch.nested_p2m[i];
+        if ( p2m->np2m_base != P2M_BASE_EADDR )
+            p2m_flush_table(p2m);
+    }
 }
 
 struct p2m_domain *
-- 
2.1.4


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