Hi Julien,
One clarification.
On 04/03/2022 10:39, Julien Grall wrote:
Hi Ayan,
On 01/03/2022 12:40, Ayan Kumar Halder wrote:
If the abort was caused due to access to stage1 translation table, Xen
will assume that the stage1 translation table is in the non MMIO region.
It will try to resolve the translation fault. If it succeeds, it will
return to the guest to retry the instruction. If not, then it means
that the table is in MMIO region which is not expected by Xen. Thus,
Xen will forward the abort to the guest.
Signed-off-by: Ayan Kumar Halder <ayank...@xilinx.com>
---
Changelog :-
v1..v8 - NA
v9 - 1. Extracted this change from "[XEN v8 2/2] xen/arm64: io: Support
instructions (for which ISS is not..." into a separate patch of its own.
The reason being this is an existing bug in the codebase.
xen/arch/arm/io.c | 11 +++++++++++
xen/arch/arm/traps.c | 12 +++++++++++-
2 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/xen/arch/arm/io.c b/xen/arch/arm/io.c
index bea69ffb08..ebcb8ed548 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
in the MMIO
+ * region. This is not expected by Xen and thus it forwards the
abort to the
We don't know that. We only know that there are no corresponding valid
mapping in the P2M. So the address may be part of an emulated MMIO
region or invalid.
For both cases, we will want to send an abort.
Furthermore, I would say "emulated MMIO region" rather than MMIO
region because the P2M can also contain MMIO mapping (we usually call
then "direct MMIO").
Can I say MMIO region (to indicate both emulated and direct) ? The
reason being the assumption that stage1 page tables cannot be in the
MMIO region. And thus, when check_p2m() is invoked, we do not invoke
try_map_mmio(gaddr_to_gfn(gpa).
See this snippet :-
if ( xabt.s1ptw )
check_mmio_region = false;
if ( check_p2m((is_data && check_mmio_region), gpa) )
return;
- Ayan
Cheers,
