xen/arm64: io: Handle the abort due to access to stage1 translation table

If the abort was caused due to access to stage1 translation table, Xen
will try to set the p2m entry (assuming that the Stage 1 translation
table is in the non MMIO region).
If there is no such entry found, then Xen will try to map the address as
a MMIO region (assuming that the Stage 1 translation table is in the
direct MMIO region).

If that fails as well, then there are the two following scenarios:-
1. Stage 1 translation table being in an emulated MMIO region - Xen
can read the region, but it has no way to return the value read to the
CPU page table walker (which tries to go through the stage1 tables to
resolve the translation fault).

2. Stage 1 translation table address is invalid.

In both the above scenarios, Xen will forward the abort to the guest.

Signed-off-by: Ayan Kumar Halder <ayankuma@xilinx.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>

diff --git a/xen/arch/arm/io.c b/xen/arch/arm/io.c
index fd903b7b035a0565a74f61e81367c55219259e80..53729a342bdabbf32cf735b1ad335cb4f263aca7 100644 (file)
--- a/xen/arch/arm/io.c
+++ b/xen/arch/arm/io.c
@@ -128,6 +128,17 @@ void try_decode_instruction(const struct cpu_user_regs *regs,
         return;
     }
 
+    /*
+     * At this point, we know that the stage1 translation table is either in
+     * an emulated MMIO region or its address is invalid. This is not
+     * expected by Xen and thus it forwards the abort to the guest.
+     */
+    if ( info->dabt.s1ptw )
+    {
+        info->dabt_instr.state = INSTR_ERROR;
+        return;
+    }
+
     /*
      * Armv8 processor does not provide a valid syndrome for decoding some
      * instructions. So in order to process these instructions, Xen must