[Xen-changelog] [xen master] xen/arm32: Use alternative to skip the check of pending serrors

[patchbot@xxxxxxx]

commit 2f08a16b043822ec9011397acf8d2a63e6802c6c
Author:     Wei Chen <Wei.Chen@xxxxxxx>
AuthorDate: Wed Apr 5 17:09:12 2017 +0800
Commit:     Stefano Stabellini <sstabellini@xxxxxxxxxx>
CommitDate: Wed Apr 5 12:12:33 2017 -0700

    xen/arm32: Use alternative to skip the check of pending serrors
    
    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. This will add overhead to check
    the option at every trap.
    
    The ARM32 supports the alternative patching feature. We can use an
    ALTERNATIVE to avoid checking option at every trap. We added a new
    cpufeature named "SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT". This feature
    will be enabled when the option is not diverse.
    
    Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
    Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
---
 xen/arch/arm/arm32/entry.S | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/xen/arch/arm/arm32/entry.S b/xen/arch/arm/arm32/entry.S
index 2187226..8cd2123 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/alternative.h>
 #include <public/xen.h>
 
 #define SAVE_ONE_BANKED(reg)    mrs r11, reg; str r11, [sp, #UREGS_##reg]
@@ -44,6 +45,14 @@ 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);
+
+        /*
+         * If the SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT has been set in the cpu
+         * feature, the checking of pending SErrors will be skipped.
+         */
+        ALTERNATIVE("nop",
+                    "b skip_check",
+                    SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT)
         /*
          * Start to check pending virtual abort in the gap of Guest -> HYP
          * world switch.
@@ -99,6 +108,7 @@ abort_guest_exit_end:
          */
         bne return_from_trap
 
+skip_check:
         mov pc, lr
 
 #define DEFINE_TRAP_ENTRY(trap)                                         \
--
generated by git-patchbot for /home/xen/git/xen.git#master

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxx
https://lists.xenproject.org/xen-changelog