Re: [Qemu-devel] [PATCH v3 0/6] block: Add VFIO based driver for NVMe device

[Fam Zheng <famz@redhat.com>]

On Thu, 07/06 16:22, Paolo Bonzini wrote:
> 
> 
> On 06/07/2017 16:06, no-reply@patchew.org wrote:
> > ERROR: Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt
> > #843: FILE: block/nvme.c:40:
> > +    volatile uint32_t *doorbell;
> > 
> > ERROR: Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt
> > #869: FILE: block/nvme.c:66:
> > +typedef volatile struct {
> 
> Indeed volatile should not be necessary, since we use memory barriers
> appropriately.  But these are hardware registers (like, host hardware)
> so I guess it's okay for this special case.

I think I used it because we don't have ACCESS_ONCE (maybe we should?).

Fam