[Qemu-devel] [PATCH qom-cpu for-2.0] cpu: Avoid QOM casts for CPU()

["Andreas Färber" <afaerber@suse.de>]

CPU address spaces touching load and store helpers as well as the
movement of (almost) all fields from CPU_COMMON to CPUState have led to
a noticeable increase of CPU() usage in "hot" paths for both TCG and KVM.

While CPU()'s OBJECT_CHECK() might help detect development errors, i.e. in
form of crashes due to QOM vs. non-QOM mismatches rather than QOM type
mismatches, it is not really needed at runtime since mostly used in
CPU-specific paths, coming from a target-specific CPU subtype. If that
pointer is damaged, other errors are highly likely occur elsewhere anyway.

Keep the CPU() macro for a consistent developer experience and
flexibility to exchange its implementation, but turn it into a pure
C cast for now.

Reported-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
---
 include/qom/cpu.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index f99885a..0aa1bdc 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -53,7 +53,7 @@ typedef uint64_t vaddr;
 
 #define TYPE_CPU "cpu"
 
-#define CPU(obj) OBJECT_CHECK(CPUState, (obj), TYPE_CPU)
+#define CPU(obj) ((CPUState *)(obj))
 #define CPU_CLASS(class) OBJECT_CLASS_CHECK(CPUClass, (class), TYPE_CPU)
 #define CPU_GET_CLASS(obj) OBJECT_GET_CLASS(CPUClass, (obj), TYPE_CPU)
 
-- 
1.8.4.5