[Xen-devel] [PATCH v2] arm/mem_access: don't reinject stage 2 access exceptions

[Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>]

The only way a guest may trip with stage 2 access violation is if mem_access is
or was in-use, so reinjecting these exceptions to the guest is never required.

Requested-by: Julien Grall <julien.grall@xxxxxxx>
Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>
---
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Julien Grall <julien.grall@xxxxxxx>

v2: simplify the patch by never reinjecting the exception
---
 xen/arch/arm/traps.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index f509a00..da951c0 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -2415,11 +2415,12 @@ static void do_trap_instr_abort_guest(struct 
cpu_user_regs *regs,
                 goto bad_insn_abort;
         }
 
-        rc = p2m_mem_access_check(gpa, gva, npfec);
-
-        /* Trap was triggered by mem_access, work here is done */
-        if ( !rc )
-            return;
+        p2m_mem_access_check(gpa, gva, npfec);
+        /*
+         * The only way to get here right now is because of mem_access,
+         * thus reinjecting the exception to the guest is never required.
+         */
+        return;
     }
     break;
     }
@@ -2462,11 +2463,12 @@ static void do_trap_data_abort_guest(struct 
cpu_user_regs *regs,
             .kind = dabt.s1ptw ? npfec_kind_in_gpt : npfec_kind_with_gla
         };
 
-        rc = p2m_mem_access_check(info.gpa, info.gva, npfec);
-
-        /* Trap was triggered by mem_access, work here is done */
-        if ( !rc )
-            return;
+        p2m_mem_access_check(info.gpa, info.gva, npfec);
+        /*
+         * The only way to get here right now is because of mem_access,
+         * thus reinjecting the exception to the guest is never required.
+         */
+        return;
     }
     break;
     }
-- 
2.8.1


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