[Xen-devel] [PATCH] mem_access: Fix npfec.kind propagation

[George Dunlap <george.dunlap@xxxxxxxxxx>]

The name of the "with_gla" flag is confusing; it has nothing to do
with the existence or lack thereof of a faulting GLA, but rather where
the fault originated.  The npfec.kind value is always valid, and
should thus be propagated, regardless of whether gla_valid is set or
not.

In particular, gla_valid will never be set on AMD systems; but
npfec.kind will still be valid and should still be propagated.

Signed-off-by: Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx>
Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxx>
---
Changes since RFC:
- Use switch() rather than a series of if's
- Adjust spacing

CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Jan Beulich <jbeulich@xxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
CC: Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>
CC: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
---
 xen/arch/x86/mm/mem_access.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/mm/mem_access.c b/xen/arch/x86/mm/mem_access.c
index d9e64fcbb9..99232045a9 100644
--- a/xen/arch/x86/mm/mem_access.c
+++ b/xen/arch/x86/mm/mem_access.c
@@ -228,16 +228,24 @@ bool p2m_mem_access_check(paddr_t gpa, unsigned long gla,
         req->reason = VM_EVENT_REASON_MEM_ACCESS;
         req->u.mem_access.gfn = gfn_x(gfn);
         req->u.mem_access.offset = gpa & ((1 << PAGE_SHIFT) - 1);
+
         if ( npfec.gla_valid )
         {
             req->u.mem_access.flags |= MEM_ACCESS_GLA_VALID;
             req->u.mem_access.gla = gla;
+        }
 
-            if ( npfec.kind == npfec_kind_with_gla )
-                req->u.mem_access.flags |= MEM_ACCESS_FAULT_WITH_GLA;
-            else if ( npfec.kind == npfec_kind_in_gpt )
-                req->u.mem_access.flags |= MEM_ACCESS_FAULT_IN_GPT;
+        switch ( npfec.kind )
+        {
+        case npfec_kind_with_gla:
+            req->u.mem_access.flags |= MEM_ACCESS_FAULT_WITH_GLA;
+            break;
+        case npfec_kind_in_gpt:
+            req->u.mem_access.flags |= MEM_ACCESS_FAULT_IN_GPT;
+        default:
+            break;
         }
+
         req->u.mem_access.flags |= npfec.read_access    ? MEM_ACCESS_R : 0;
         req->u.mem_access.flags |= npfec.write_access   ? MEM_ACCESS_W : 0;
         req->u.mem_access.flags |= npfec.insn_fetch     ? MEM_ACCESS_X : 0;
-- 
2.19.0


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