Re: [Xen-devel] [PATCH 06/10] vpci/header: add teardown cleanup

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Jun 29, 2018 at 12:15:34PM +0100, Wei Liu wrote:
> On Wed, Jun 20, 2018 at 04:42:30PM +0200, Roger Pau Monne wrote:
> > In order to unmap the BARs
> > 
> > Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> > ---
> > Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> > Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> > Cc: Jan Beulich <jbeulich@xxxxxxxx>
> > Cc: Julien Grall <julien.grall@xxxxxxx>
> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> > Cc: Tim Deegan <tim@xxxxxxx>
> > Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
> > ---
> >  xen/drivers/vpci/header.c | 30 +++++++++++++++++++++++-------
> >  1 file changed, 23 insertions(+), 7 deletions(-)
> > 
> > diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
> > index 4363270a55..686e04e35a 100644
> > --- a/xen/drivers/vpci/header.c
> > +++ b/xen/drivers/vpci/header.c
> > @@ -131,12 +131,15 @@ bool vpci_process_pending(struct vcpu *v)
> >          if ( rc == -ERESTART )
> >              return true;
> >  
> > -        spin_lock(&v->vpci.pdev->vpci_lock);
> > -        if ( v->vpci.pdev->vpci )
> > -            /* Disable memory decoding unconditionally on failure. */
> > -            modify_decoding(v->vpci.pdev, !rc && v->vpci.map,
> > -                            !rc && v->vpci.rom_only);
> > -        spin_unlock(&v->vpci.pdev->vpci_lock);
> > +        if ( v->vpci.pdev )
> > +        {
> > +            spin_lock(&v->vpci.pdev->vpci_lock);
> > +            if ( v->vpci.pdev->vpci )
> > +                /* Disable memory decoding unconditionally on failure. */
> > +                modify_decoding(v->vpci.pdev, !rc && v->vpci.map,
> > +                                !rc && v->vpci.rom_only);
> > +            spin_unlock(&v->vpci.pdev->vpci_lock);
> > +        }
> >  
> >          rangeset_destroy(v->vpci.mem);
> >          v->vpci.mem = NULL;
> > @@ -560,7 +563,20 @@ static int init_bars(struct pci_dev *pdev)
> >  
> >      return (cmd & PCI_COMMAND_MEMORY) ? modify_bars(pdev, true, false) : 0;
> >  }
> > -REGISTER_VPCI_INIT(init_bars, NULL, VPCI_PRIORITY_MIDDLE);
> > +
> > +static void teardown_bars(struct pci_dev *pdev)
> > +{
> > +    uint16_t cmd = pci_conf_read16(pdev->seg, pdev->bus, 
> > PCI_SLOT(pdev->devfn),
> > +                                   PCI_FUNC(pdev->devfn), PCI_COMMAND);
> > +
> > +    if ( cmd & PCI_COMMAND_MEMORY )
> > +    {
> > +        /* Unmap all BARs from guest p2m. */
> > +        modify_bars(pdev, false, false);
> 
> So modify_bars will eventually call defer_map in most cases (which I
> believe are the ones your care about here).
> 
> But then the following line sets vpci.pdev to NULL, which means the
> check in vpci_process_pending is false and modify_decoding is skipped.
> If that what you want?

Yes, after the call to teardown_bars the pdev can be removed, so the
deferred part of the unmap shouldn't rely on pdev being available.
That means that the memory decoding bit is not switched off. I would
expect that the device will get reset into a proper state (or in the
SR-IOV just disappear).

Trying to get the state of the device to the same state it was when
vpci was activated doesn't seem very feasible.

Thanks, Roger.

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