Am 28.03.2014 16:52, schrieb Peter Maydell: > On 28 March 2014 15:49, Andreas Färber <afaer...@suse.de> wrote: >> 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.
"to occur" >> >> Keep the CPU() macro for a consistent developer experience and "and for" >> flexibility to exchange its implementation, but turn it into a pure >> C cast for now. >> >> Reported-by: Laurent Desnogues <laurent.desnog...@gmail.com> >> Suggested-by: Paolo Bonzini <pbonz...@redhat.com> >> Signed-off-by: Andreas Färber <afaer...@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) /* Avoid unnecessary penalties in hot paths 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) >> >> -- >> 1.8.4.5 > > Not important if we're going to revert this as soon as 2.0 > is out of the door, but if we expect this to be around for > longer than that it would be worth a brief comment explaining > why this cast macro is a special case. Right now I don't see a post-2.0 solution emerging, so yes, documentation is good. Cheers, Andreas -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg
