[Xen-devel] [PATCH 10/18] xen/arm32: Use cpu_hwcaps to skip the check of pending serrors

[Wei Chen <Wei.Chen@xxxxxxx>]

We have provided an option to administrator to determine how to
handle the SErrors. In order to skip the check of pending SError,
in conventional way, we have to read the option every time before
we try to check the pending SError.

Currently, we haven't export the option to other source file. But,
in the previous patch, we had set "SKIP_CHECK_PENDING_VSERROR" to
cpu_hwcaps when the option doesn't need to check the SErrors. So we
can use checking cpu_hwcaps to replace checking the option directly.

Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>

---
This is a temporary solution, this would have to be dropped as soon
as ARM32 gain support of alternative patching to avoid potential misusage.
The alternative patching support patches for ARM32 are still in review
stage.
---
 xen/arch/arm/arm32/entry.S | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/xen/arch/arm/arm32/entry.S b/xen/arch/arm/arm32/entry.S
index 2187226..79929ca 100644
--- a/xen/arch/arm/arm32/entry.S
+++ b/xen/arch/arm/arm32/entry.S
@@ -1,5 +1,6 @@
 #include <asm/asm_defns.h>
 #include <asm/regs.h>
+#include <asm/cpufeature.h>
 #include <public/xen.h>
 
 #define SAVE_ONE_BANKED(reg)    mrs r11, reg; str r11, [sp, #UREGS_##reg]
@@ -11,6 +12,21 @@
 #define RESTORE_BANKED(mode) \
         RESTORE_ONE_BANKED(SP_##mode) ; RESTORE_ONE_BANKED(LR_##mode) ; 
RESTORE_ONE_BANKED(SPSR_##mode)
 
+/*
+ * If the SKIP_CHECK_PENDING_VSERROR has been set in the cpu feature,
+ * the checking of pending SErrors will be skipped.
+ *
+ * As it is a temporary solution, we are assuming that
+ * SKIP_CHECK_PENDING_VSERROR will always be in the first word for
+ * cpu_hwcaps. This would have to be dropped as soon as ARM32 gain
+ * support of alternative.
+ */
+#define SKIP_VSERROR_CHECK                      \
+        ldr r1, =cpu_hwcaps;                    \
+        ldr r1, [r1];                           \
+        tst r1, #SKIP_CHECK_PENDING_VSERROR;    \
+        moveq pc, lr
+
 #define SAVE_ALL                                                        \
         sub sp, #(UREGS_SP_usr - UREGS_sp); /* SP, LR, SPSR, PC */      \
         push {r0-r12}; /* Save R0-R12 */                                \
@@ -44,6 +60,9 @@ save_guest_regs:
         SAVE_BANKED(fiq)
         SAVE_ONE_BANKED(R8_fiq); SAVE_ONE_BANKED(R9_fiq); 
SAVE_ONE_BANKED(R10_fiq)
         SAVE_ONE_BANKED(R11_fiq); SAVE_ONE_BANKED(R12_fiq);
+
+        SKIP_VSERROR_CHECK
+
         /*
          * Start to check pending virtual abort in the gap of Guest -> HYP
          * world switch.
-- 
2.7.4


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