[Xen-devel] [PATCH 18 of 36] x86/paravirt: add debugging for missing operations

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

Rather than just jumping to 0 when there's a missing operation, raise a BUG.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 arch/x86/Kconfig           |    7 +++++++
 include/asm-x86/paravirt.h |    8 ++++++++
 2 files changed, 15 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -433,6 +433,13 @@
          the kernel is theoretically slower and slightly larger.
 
 endif
+
+config PARAVIRT_DEBUG
+       bool "paravirt-ops debugging"
+       depends on PARAVIRT && DEBUG_KERNEL
+       help
+         Enable to debug paravirt_ops internals.  Specifically, BUG if
+        a paravirt_op is missing when it is called.
 
 config MEMTEST
        bool "Memtest"
diff --git a/include/asm-x86/paravirt.h b/include/asm-x86/paravirt.h
--- a/include/asm-x86/paravirt.h
+++ b/include/asm-x86/paravirt.h
@@ -460,10 +460,17 @@
 #define VEXTRA_CLOBBERS         , "rax", "r8", "r9", "r10", "r11"
 #endif
 
+#ifdef CONFIG_PARAVIRT_DEBUG
+#define PVOP_TEST_NULL(op)     BUG_ON(op == NULL)
+#else
+#define PVOP_TEST_NULL(op)     ((void)op)
+#endif
+
 #define __PVOP_CALL(rettype, op, pre, post, ...)                       \
        ({                                                              \
                rettype __ret;                                          \
                PVOP_CALL_ARGS;                                 \
+               PVOP_TEST_NULL(op);                                     \
                /* This is 32-bit specific, but is okay in 64-bit */    \
                /* since this condition will never hold */              \
                if (sizeof(rettype) > sizeof(unsigned long)) {          \
@@ -492,6 +499,7 @@
 #define __PVOP_VCALL(op, pre, post, ...)                               \
        ({                                                              \
                PVOP_VCALL_ARGS;                                        \
+               PVOP_TEST_NULL(op);                                     \
                asm volatile(pre                                        \
                             paravirt_alt(PARAVIRT_CALL)                \
                             post                                       \



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