[Xen-changelog] [xen master] xen/arm64: Use alternative to skip the check of pending serrors

[patchbot@xxxxxxx]

commit a61573f4f17a09de1f8ab761235842531b957337
Author:     Wei Chen <Wei.Chen@xxxxxxx>
AuthorDate: Wed Apr 5 17:09:11 2017 +0800
Commit:     Stefano Stabellini <sstabellini@xxxxxxxxxx>
CommitDate: Wed Apr 5 12:12:29 2017 -0700

    xen/arm64: 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 ARM64 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: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 xen/arch/arm/arm64/entry.S | 41 +++++++++++++++++++++++++----------------
 1 file changed, 25 insertions(+), 16 deletions(-)

diff --git a/xen/arch/arm/arm64/entry.S b/xen/arch/arm/arm64/entry.S
index 02802c0..3d2fdfb 100644
--- a/xen/arch/arm/arm64/entry.S
+++ b/xen/arch/arm/arm64/entry.S
@@ -1,5 +1,6 @@
 #include <asm/asm_defns.h>
 #include <asm/regs.h>
+#include <asm/alternative.h>
 #include <public/xen.h>
 
 /*
@@ -229,12 +230,14 @@ hyp_irq:
 
 guest_sync:
         entry   hyp=0, compat=0
-        bl      check_pending_vserror
         /*
-         * If x0 is Non-zero, a vSError took place, the initial exception
-         * doesn't have any significance to be handled. Exit ASAP
+         * The vSError will be checked while SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT
+         * is not set. If a vSError took place, the initial exception will be
+         * skipped. Exit ASAP
          */
-        cbnz    x0, 1f
+        ALTERNATIVE("bl check_pending_vserror; cbnz x0, 1f",
+                    "nop; nop",
+                    SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT)
         msr     daifclr, #2
         mov     x0, sp
         bl      do_trap_hypervisor
@@ -243,12 +246,14 @@ guest_sync:
 
 guest_irq:
         entry   hyp=0, compat=0
-        bl      check_pending_vserror
         /*
-         * If x0 is Non-zero, a vSError took place, the initial exception
-         * doesn't have any significance to be handled. Exit ASAP
+         * The vSError will be checked while SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT
+         * is not set. If a vSError took place, the initial exception will be
+         * skipped. Exit ASAP
          */
-        cbnz    x0, 1f
+        ALTERNATIVE("bl check_pending_vserror; cbnz x0, 1f",
+                    "nop; nop",
+                    SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT)
         mov     x0, sp
         bl      do_trap_irq
 1:
@@ -267,12 +272,14 @@ guest_error:
 
 guest_sync_compat:
         entry   hyp=0, compat=1
-        bl      check_pending_vserror
         /*
-         * If x0 is Non-zero, a vSError took place, the initial exception
-         * doesn't have any significance to be handled. Exit ASAP
+         * The vSError will be checked while SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT
+         * is not set. If a vSError took place, the initial exception will be
+         * skipped. Exit ASAP
          */
-        cbnz    x0, 1f
+        ALTERNATIVE("bl check_pending_vserror; cbnz x0, 1f",
+                    "nop; nop",
+                    SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT)
         msr     daifclr, #2
         mov     x0, sp
         bl      do_trap_hypervisor
@@ -281,12 +288,14 @@ guest_sync_compat:
 
 guest_irq_compat:
         entry   hyp=0, compat=1
-        bl      check_pending_vserror
         /*
-         * If x0 is Non-zero, a vSError took place, the initial exception
-         * doesn't have any significance to be handled. Exit ASAP
+         * The vSError will be checked while SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT
+         * is not set. If a vSError took place, the initial exception will be
+         * skipped. Exit ASAP
          */
-        cbnz    x0, 1f
+        ALTERNATIVE("bl check_pending_vserror; cbnz x0, 1f",
+                    "nop; nop",
+                    SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT)
         mov     x0, sp
         bl      do_trap_irq
 1:
--
generated by git-patchbot for /home/xen/git/xen.git#master

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