[Xen-changelog] [xen master] xen/arm: Provide macros to help creating workaround helpers

[patchbot@xxxxxxx]

commit 238ea8b2338d1465a244681e47bfc1172102dd6d
Author:     Julien Grall <julien.grall@xxxxxxx>
AuthorDate: Thu Aug 4 18:50:03 2016 +0100
Commit:     Stefano Stabellini <sstabellini@xxxxxxxxxx>
CommitDate: Thu Aug 4 10:55:03 2016 -0700

    xen/arm: Provide macros to help creating workaround helpers
    
    Workarounds may require to execute a different path when the platform
    is affected by the associated erratum. Furthermore, this may need to
    be called in the common code.
    
    To avoid too much intrusion/overhead, the workaround helpers need to
    be a nop on architecture which will never have the workaround and have
    to be quick to check whether the platform requires it.
    
    The alternative framework is used to transform the check in a single
    instruction. When the framework is not available, the helper will have
    ~6 instructions including 1 instruction load.
    
    The macro will create a handler called check_workaround_xxxxx with
    xxxx the erratum number.
    
    For instance, the line bellow will create a workaround helper for
    erratum #424242 which is enabled when the capability
    ARM64_WORKAROUND_424242 is set and only available for ARM64:
    
    CHECK_WORKAROUND_HELPER(424242, ARM64_WORKAROUND_42424242, CONFIG_ARM64)
    
    Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
    Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
    Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 xen/include/asm-arm/cpuerrata.h | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/xen/include/asm-arm/cpuerrata.h b/xen/include/asm-arm/cpuerrata.h
index c495ee5..2982a92 100644
--- a/xen/include/asm-arm/cpuerrata.h
+++ b/xen/include/asm-arm/cpuerrata.h
@@ -1,8 +1,47 @@
 #ifndef __ARM_CPUERRATA_H__
 #define __ARM_CPUERRATA_H__
 
+#include <xen/config.h>
+#include <asm/cpufeature.h>
+#include <asm/alternative.h>
+
 void check_local_cpu_errata(void);
 
+#ifdef CONFIG_ALTERNATIVE
+
+#define CHECK_WORKAROUND_HELPER(erratum, feature, arch)         \
+static inline bool_t check_workaround_##erratum(void)           \
+{                                                               \
+    if ( !IS_ENABLED(arch) )                                    \
+        return 0;                                               \
+    else                                                        \
+    {                                                           \
+        bool_t ret;                                             \
+                                                                \
+        asm volatile (ALTERNATIVE("mov %0, #0",                 \
+                                  "mov %0, #1",                 \
+                                  feature)                      \
+                      : "=r" (ret));                            \
+                                                                \
+        return unlikely(ret);                                   \
+    }                                                           \
+}
+
+#else /* CONFIG_ALTERNATIVE */
+
+#define CHECK_WORKAROUND_HELPER(erratum, feature, arch)         \
+static inline bool_t check_workaround_##erratum(void)           \
+{                                                               \
+    if ( !IS_ENABLED(arch) )                                    \
+        return 0;                                               \
+    else                                                        \
+        return unlikely(cpus_have_cap(feature));                \
+}
+
+#endif
+
+#undef CHECK_WORKAROUND_HELPER
+
 #endif /* __ARM_CPUERRATA_H__ */
 /*
  * Local variables:
--
generated by git-patchbot for /home/xen/git/xen.git#master

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