Il 26/03/2014 14:42, Paolo Bonzini ha scritto:
QOM casts are only typesafe inasmuch as we know that the argument is
a QOM object. If it is not, the accesses to fields in Object can
access invalid memory and thus cause a segfault.
Using a QOM cast in ENV_GET_CPU is useless and harmful. Useless,
because the cast is applied to the result of container_of, which is
type safe. So the QOM cast is nothing but typesafety theater.
Harmful, because ENV_GET_CPU *is* used in hot paths especially
now that, in 2.0, the movement of fields from CPU_COMMON to
CPUState was completed.
Reported-by: Laurent Desnogues <laurent.desnog...@gmail.com>
Cc: Andreas Faerber <afaer...@suse.de>
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
Andreas pointed out on IRC that this is just the tip of the iceberg, due
to code like this:
static void vmsa_ttbcr_write(CPUARMState *env, const ARMCPRegInfo *ri,
uint64_t value)
{
ARMCPU *cpu = arm_env_get_cpu(env);
if (arm_feature(env, ARM_FEATURE_LPAE)) {
/* With LPAE the TTBCR could result in a change of ASID
* via the TTBCR.A1 bit, so do a TLB flush.
*/
tlb_flush(CPU(cpu), 1);
}
vmsa_ttbcr_raw_write(env, ri, value);
}
(from target-arm/helper.c). Given this, and the limited time to fix the
problem in 2.0 where it got magnified, I think we should reconsider
whether releases should ahve QOM cast debugging enabled.
Paolo
