Re: [Qemu-devel] [PATCH 26/32] ppc: Speed up dcbz

[Benjamin Herrenschmidt]

On Wed, 2016-07-27 at 12:36 +1000, David Gibson wrote:
> > -    do_dcbz(env, addr, dcbz_size, GETPC());
> > +    /* Try fast path translate */
> > +    haddr = tlb_vaddr_to_host(env, addr, MMU_DATA_STORE, env->dmmu_idx);
> 
> It worries me slightly that this doesn't take any length to verify.  I
> guess it's ok in practice, because memory blocks will always be at
> least cache line size aligned.

It's safe ;-)

The translate returns a qemu page size address which is always 4K.

We don't need to verify  because we just aligned the address to the
cache block size which is always smaller than 4k. So we can't
possibly be crossing a page boundary.

(grep for tlb_vaddr_to_host in target-s390 for other examples of use
of tlb_vaddr_to_host).

Cheers,
Ben.