Re: [Xen-devel] [PATCH v2] xen/pt: Fix a xen passthrough failure

[Zhao Yan <yan.y.zhao@xxxxxxxxx>]

On Mon, Dec 03, 2018 at 12:20:30PM +0100, Roger Pau Monné wrote:
> Hello,
> 
> Thanks for the patch.
> 
> The subject should be more descriptive, "Fix a xen passthrough
> failure" is too generic. How about: "allow passthrough of devices with
> bogus interrupt pin" or something similar.
right, thanks for your suggestion. I'll change the subject to this one.

> 
> On Mon, Dec 03, 2018 at 12:04:38AM -0500, Zhao Yan wrote:
> > For some pci device, even its PCI_INTERRUPT_PIN is not 0, it actually
> > doesn't support INTx mode, so its machine irq read from host sysfs is 0.
> > In that case, report PCI_INTERRUPT_PIN as 0 to guest and let passthrough
> > continue.
> > 
> > v2: fix some coding style issue
> 
> The changelog between versions should be below the '---'.
> 
got it. thanks :)

> > 
> > Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> > Cc: Jan Beulich <JBeulich@xxxxxxxx>
> > Signed-off-by: Zhao Yan <yan.y.zhao@xxxxxxxxx>
> > ---
> >  hw/xen/xen_pt.c             | 5 +++++
> >  hw/xen/xen_pt_config_init.c | 8 +++++++-
> >  2 files changed, 12 insertions(+), 1 deletion(-)
> > 
> > diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
> > index f1f3a3727c..d601c9979c 100644
> > --- a/hw/xen/xen_pt.c
> > +++ b/hw/xen/xen_pt.c
> > @@ -847,6 +847,11 @@ static void xen_pt_realize(PCIDevice *d, Error **errp)
> >      }
> >  
> >      machine_irq = s->real_device.irq;
> > +    if (machine_irq == 0) {
> > +        XEN_PT_LOG(d, "machine irq is 0\n");
> 
> I would maybe consider disabling INTX assertion here on the command
> register.
> 
ok, I'll add that.
Actually I was vacillating on whether to add the disabling of INTx
assertion, as I thought PCI_INTERRUPT_PIN was already reported 0. 
But adding the disabling is better.


> > +        goto out;
> > +    }
> > +
> >      rc = xc_physdev_map_pirq(xen_xc, xen_domid, machine_irq, &pirq);
> >      if (rc < 0) {
> >          error_setg_errno(errp, errno, "Mapping machine irq %u to"
> > diff --git a/hw/xen/xen_pt_config_init.c b/hw/xen/xen_pt_config_init.c
> > index 47f9010c75..1007b6c977 100644
> > --- a/hw/xen/xen_pt_config_init.c
> > +++ b/hw/xen/xen_pt_config_init.c
> > @@ -300,7 +300,13 @@ static int 
> > xen_pt_irqpin_reg_init(XenPCIPassthroughState *s,
> >                                    XenPTRegInfo *reg, uint32_t real_offset,
> >                                    uint32_t *data)
> >  {
> > -    *data = xen_pt_pci_read_intx(s);
> > +    if (s->real_device.irq)
> > +        *data = xen_pt_pci_read_intx(s);
> > +    else {
> > +        XEN_PT_LOG(&s->dev,
> > +            "machine irq is 0, init guest PCI_INTERRUPT_PIN to 0\n");
> > +        *data = 0;
> 
> The default value for the register is already zero, so you could drop
> the else branch AFAICT.
ok, I'll drop the else branch. thanks for your review :)


> Thanks, Roger.

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