[Xen-devel] [PATCH 14/18] xen/arm: Unmask the Abort/SError bit in the exception entries

[Wei Chen <Wei.Chen@xxxxxxx>]

Currently, we masked the Abort/SError bit in Xen exception entries.
So Xen could not capture any Abort/SError while it's running.
Now, Xen has the ability to handle the Abort/SError, we should unmask
the Abort/SError bit by default to let Xen capture Abort/SError while
it's running.

But in order to avoid receiving nested asynchronous abort, we don't
unmask Abort/SError bit in hyp_error and trap_data_abort.

Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
---
We haven't done this before, so I don't know how can this change
will affect the Xen. If the IRQ and Abort take place at the same
time, how can we handle them? If an abort is taking place while we're
handling the IRQ, the program jump to abort exception, and then enable
the IRQ. In this case, what will happen? So I think I need more
discussions from community.
---
 xen/arch/arm/arm32/entry.S | 15 ++++++++++++++-
 xen/arch/arm/arm64/entry.S | 13 ++++++++-----
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/xen/arch/arm/arm32/entry.S b/xen/arch/arm/arm32/entry.S
index 79929ca..4d46239 100644
--- a/xen/arch/arm/arm32/entry.S
+++ b/xen/arch/arm/arm32/entry.S
@@ -125,6 +125,7 @@ abort_guest_exit_end:
 trap_##trap:                                                            \
         SAVE_ALL;                                                       \
         cpsie i;        /* local_irq_enable */                          \
+        cpsie a;        /* asynchronous abort enable */                 \
         adr lr, return_from_trap;                                       \
         mov r0, sp;                                                     \
         mov r11, sp;                                                    \
@@ -135,6 +136,18 @@ trap_##trap:                                               
             \
         ALIGN;                                                          \
 trap_##trap:                                                            \
         SAVE_ALL;                                                       \
+        cpsie a;        /* asynchronous abort enable */                 \
+        adr lr, return_from_trap;                                       \
+        mov r0, sp;                                                     \
+        mov r11, sp;                                                    \
+        bic sp, #7; /* Align the stack pointer (noop on guest trap) */  \
+        b do_trap_##trap
+
+#define DEFINE_TRAP_ENTRY_NOABORT(trap)                                 \
+        ALIGN;                                                          \
+trap_##trap:                                                            \
+        SAVE_ALL;                                                       \
+        cpsie i;        /* local_irq_enable */                          \
         adr lr, return_from_trap;                                       \
         mov r0, sp;                                                     \
         mov r11, sp;                                                    \
@@ -155,10 +168,10 @@ GLOBAL(hyp_traps_vector)
 DEFINE_TRAP_ENTRY(undefined_instruction)
 DEFINE_TRAP_ENTRY(supervisor_call)
 DEFINE_TRAP_ENTRY(prefetch_abort)
-DEFINE_TRAP_ENTRY(data_abort)
 DEFINE_TRAP_ENTRY(hypervisor)
 DEFINE_TRAP_ENTRY_NOIRQ(irq)
 DEFINE_TRAP_ENTRY_NOIRQ(fiq)
+DEFINE_TRAP_ENTRY_NOABORT(data_abort)
 
 return_from_trap:
         mov sp, r11
diff --git a/xen/arch/arm/arm64/entry.S b/xen/arch/arm/arm64/entry.S
index 8d5a890..0401a41 100644
--- a/xen/arch/arm/arm64/entry.S
+++ b/xen/arch/arm/arm64/entry.S
@@ -187,13 +187,14 @@ hyp_error:
 /* Traps taken in Current EL with SP_ELx */
 hyp_sync:
         entry   hyp=1
-        msr     daifclr, #2
+        msr     daifclr, #6
         mov     x0, sp
         bl      do_trap_hypervisor
         exit    hyp=1
 
 hyp_irq:
         entry   hyp=1
+        msr     daifclr, #4
         mov     x0, sp
         bl      do_trap_irq
         exit    hyp=1
@@ -208,7 +209,7 @@ guest_sync:
         ALTERNATIVE("bl check_pending_vserror; cbnz x0, 1f",
                     "nop; nop",
                     SKIP_CHECK_PENDING_VSERROR)
-        msr     daifclr, #2
+        msr     daifclr, #6
         mov     x0, sp
         bl      do_trap_hypervisor
 1:
@@ -224,6 +225,7 @@ guest_irq:
         ALTERNATIVE("bl check_pending_vserror; cbnz x0, 1f",
                     "nop; nop",
                     SKIP_CHECK_PENDING_VSERROR)
+        msr     daifclr, #4
         mov     x0, sp
         bl      do_trap_irq
 1:
@@ -235,7 +237,7 @@ guest_fiq_invalid:
 
 guest_error:
         entry   hyp=0, compat=0
-        msr     daifclr, #2
+        msr     daifclr, #6
         mov     x0, sp
         bl      do_trap_guest_serror
         exit    hyp=0, compat=0
@@ -250,7 +252,7 @@ guest_sync_compat:
         ALTERNATIVE("bl check_pending_vserror; cbnz x0, 1f",
                     "nop; nop",
                     SKIP_CHECK_PENDING_VSERROR)
-        msr     daifclr, #2
+        msr     daifclr, #6
         mov     x0, sp
         bl      do_trap_hypervisor
 1:
@@ -266,6 +268,7 @@ guest_irq_compat:
         ALTERNATIVE("bl check_pending_vserror; cbnz x0, 1f",
                     "nop; nop",
                     SKIP_CHECK_PENDING_VSERROR)
+        msr     daifclr, #4
         mov     x0, sp
         bl      do_trap_irq
 1:
@@ -277,7 +280,7 @@ guest_fiq_invalid_compat:
 
 guest_error_compat:
         entry   hyp=0, compat=1
-        msr     daifclr, #2
+        msr     daifclr, #6
         mov     x0, sp
         bl      do_trap_guest_serror
         exit    hyp=0, compat=1
-- 
2.7.4


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