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

[patchbot@xxxxxxx]

commit fdfb07eb28e42b456e5e1ce999a47cc3ea439f7f
Author:     Ayan Kumar Halder <ayan.kumar.halder@xxxxxxxxxx>
AuthorDate: Thu Mar 17 14:00:45 2022 +0000
Commit:     Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
CommitDate: Fri Mar 18 21:17:34 2022 -0700

    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 a 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 a
    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>
    Tested-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
    Reviewed-by: Stefano Stabellini <sstabellini@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..6f458ee7fd 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#master