diff options
| author | Andreas Färber <afaerber@suse.de> | 2014-03-28 16:25:07 +0100 |
|---|---|---|
| committer | Andreas Färber <afaerber@suse.de> | 2014-03-31 19:28:38 +0200 |
| commit | 0d6d1ab4990b6e8c6f24e9b1308801d657d411ad (patch) | |
| tree | e80fcd044516d50dadf27226fb25facebb783e0a /include/qom | |
| parent | c8c14bcb72e436fb4aff99b4b2b92e44f2e715b5 (diff) | |
cpu: Avoid QOM casts for CPU()
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 to occur elsewhere
anyway.
Keep the CPU() macro for a consistent developer experience and for
flexibility to exchange its implementation, but turn it into a pure,
unchecked C cast for now.
Compare commit 6e42be7cd10260fd3a006d94f6c870692bf7a2c0.
Reported-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
Diffstat (limited to 'include/qom')
| -rw-r--r-- | include/qom/cpu.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/include/qom/cpu.h b/include/qom/cpu.h index f99885a137..df977c88f0 100644 --- a/include/qom/cpu.h +++ b/include/qom/cpu.h @@ -53,7 +53,12 @@ typedef uint64_t vaddr; #define TYPE_CPU "cpu" -#define CPU(obj) OBJECT_CHECK(CPUState, (obj), TYPE_CPU) +/* Since this macro is used a lot in hot code paths and in conjunction with + * FooCPU *foo_env_get_cpu(), we deviate from usual QOM practice by using + * an unchecked cast. + */ +#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) |