Re: [PATCH v5 05/14] hw/block/nvme: Add support for Namespace Types

[Niklas Cassel <Niklas.Cassel@wdc.com>]

On Thu, Oct 01, 2020 at 09:29:22AM -0600, Keith Busch wrote:
> On Thu, Oct 01, 2020 at 11:22:46AM +0000, Niklas Cassel wrote:
> > On Mon, Sep 28, 2020 at 11:35:19AM +0900, Dmitry Fomichev wrote:
> > > From: Niklas Cassel <niklas.cassel@wdc.com>
> > > @@ -2222,6 +2328,30 @@ static void nvme_write_bar(NvmeCtrl *n, hwaddr offset, uint64_t data,
> > >          break;
> > >      case 0x14:  /* CC */
> > >          trace_pci_nvme_mmio_cfg(data & 0xffffffff);
> > > +
> > > +        if (NVME_CC_CSS(data) != NVME_CC_CSS(n->bar.cc)) {
> > > +            if (NVME_CC_EN(n->bar.cc)) {
> > 
> > I just saw this print when doing controller reset on a live system.
> > 
> > Added a debug print:
> > nvme_write_bar WRITING: 0x0 previous: 0x464061
> > 
> > so the second if-statement has to be:
> > 
> >     if (NVME_CC_EN(n->bar.cc) && NVME_CC_EN(data)) {
> > 
> > Sorry for introducing the bug in the first place.
> 
> No worries.
> 
> I don't think the check should be here at all, really. The only check for valid
> CSS should be in nvme_start_ctrl(), which I posted yesterday.

The reasoning for this additional check is this:

From CC.CC register description:

"This field shall only be changed when the controller
is disabled (CC.EN is cleared to ‘0’)."

In the QEMU model, we have functions, e.g. nvme_cmd_effects(),
that uses n->bar.cc "at runtime".

So I don't think that simply checking for valid CSS in
nvme_start_ctrl() is sufficient.

Thoughts?


Kind regards,
Niklas

>  
> > > +                NVME_GUEST_ERR(pci_nvme_err_change_css_when_enabled,
> > > +                               "changing selected command set when enabled");
> > > +            } else {
> > > +                switch (NVME_CC_CSS(data)) {
> > > +                case CSS_NVM_ONLY:
> > > +                    trace_pci_nvme_css_nvm_cset_selected_by_host(data &
> > > +                                                                 0xffffffff);
> > > +                    break;
> > > +                case CSS_CSI:
> > > +                    NVME_SET_CC_CSS(n->bar.cc, CSS_CSI);
> > > +                    trace_pci_nvme_css_all_csets_sel_by_host(data & 0xffffffff);
> > > +                    break;
> > > +                case CSS_ADMIN_ONLY:
> > > +                    break;
> > > +                default:
> > > +                    NVME_GUEST_ERR(pci_nvme_ub_unknown_css_value,
> > > +                                   "unknown value in CC.CSS field");
> > > +                }
> > > +            }
> > > +        }