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

[patchbot@xxxxxxx]

commit fef5531fd8f311b347970568d77e7bf4feffd7fb
Author:     Ayan Kumar Halder <ayan.kumar.halder@xxxxxxxxxx>
AuthorDate: Thu Mar 10 17:45:00 2022 +0000
Commit:     Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Mon Mar 14 18:02:16 2022 +0000

    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@xxxxxxxxxx>
    Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 xen/arch/arm/io.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/xen/arch/arm/io.c b/xen/arch/arm/io.c
index fd903b7b03..53729a342b 100644
--- 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
--
generated by git-patchbot for /home/xen/git/xen.git#staging