[Xen-changelog] [xen master] xen/arm: Introduce a macro to synchronize SError

[patchbot@xxxxxxx]

commit 297e74abca4731be77801e1e725347baa5b38781
Author:     Wei Chen <Wei.Chen@xxxxxxx>
AuthorDate: Wed Apr 5 17:09:18 2017 +0800
Commit:     Stefano Stabellini <sstabellini@xxxxxxxxxx>
CommitDate: Wed Apr 5 12:14:44 2017 -0700

    xen/arm: Introduce a macro to synchronize SError
    
    In previous patches, we have provided the ability to synchronize
    SErrors in exception entries. But we haven't synchronized SErrors
    while returning to guest and doing context switch.
    
    So we still have two risks:
    1. Slipping hypervisor SErrors to guest. For example, hypervisor
       triggers a SError while returning to guest, but this SError may be
       delivered after entering guest. In "DIVERSE" option, this SError
       would be routed back to guest and panic the guest. But actually,
       we should crash the whole system due to this hypervisor SError.
    2. Slipping previous guest SErrors to the next guest. In "FORWARD"
       option, if hypervisor triggers a SError while context switching.
       This SError may be delivered after switching to next vCPU. In this
       case, this SError will be forwarded to next vCPU and may panic
       an incorrect guest.
    
    So we have have to introduce this macro to synchronize SErrors while
    returning to guest and doing context switch. In this macro, we use
    ASSERT to make sure the abort is ummasked. Because we unmasked abort
    in the entries, but we don't know whether someone will mask it in the
    future.
    
    We also added a barrier to this macro to prevent compiler reorder our
    asm volatile code.
    
    Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
    Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
    Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 xen/include/asm-arm/processor.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
index bb24bee..855ded1 100644
--- a/xen/include/asm-arm/processor.h
+++ b/xen/include/asm-arm/processor.h
@@ -723,6 +723,18 @@ void abort_guest_exit_end(void);
     ( (unsigned long)abort_guest_exit_end == (r)->pc ) \
 )
 
+/*
+ * Synchronize SError unless the feature is selected.
+ * This is relying on the SErrors are currently unmasked.
+ */
+#define SYNCHRONIZE_SERROR(feat)                                  \
+    do {                                                          \
+        ASSERT(!cpus_have_cap(feat) || local_abort_is_enabled()); \
+        asm volatile(ALTERNATIVE("dsb sy; isb",                   \
+                                 "nop; nop", feat)                \
+                                 : : : "memory");                 \
+    } while (0)
+
 #endif /* __ASSEMBLY__ */
 #endif /* __ASM_ARM_PROCESSOR_H */
 /*
--
generated by git-patchbot for /home/xen/git/xen.git#master

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