Re: [RFC XEN PATCH 2/6] vpci: accept BAR writes if dom0 is PVH

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 13 Mar 2023, Christian König wrote:
> Am 13.03.23 um 08:23 schrieb Christian König:
> > Am 12.03.23 um 08:54 schrieb Huang Rui:
> > > From: Chen Jiqian <Jiqian.Chen@xxxxxxx>
> > > 
> > > When dom0 is PVH and we want to passthrough gpu to guest,
> > > we should allow BAR writes even through BAR is mapped. If
> > > not, the value of BARs are not initialized when guest firstly
> > > start.
> > > 
> > > Signed-off-by: Chen Jiqian <Jiqian.Chen@xxxxxxx>
> > > Signed-off-by: Huang Rui <ray.huang@xxxxxxx>
> > > ---
> > >   xen/drivers/vpci/header.c | 2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
> > > index ec2e978a4e..918d11fbce 100644
> > > --- a/xen/drivers/vpci/header.c
> > > +++ b/xen/drivers/vpci/header.c
> > > @@ -392,7 +392,7 @@ static void cf_check bar_write(
> > >        * Xen only cares whether the BAR is mapped into the p2m, so allow
> > > BAR
> > >        * writes as long as the BAR is not mapped into the p2m.
> > >        */
> > > -    if ( bar->enabled )
> > > +    if ( pci_conf_read16(pdev->sbdf, PCI_COMMAND) & PCI_COMMAND_MEMORY )
> > 
> > Checkpath.pl gives here:
> > 
> > ERROR: space prohibited after that open parenthesis '('
> > #115: FILE: xen/drivers/vpci/header.c:395:
> > +    if ( pci_conf_read16(pdev->sbdf, PCI_COMMAND) & PCI_COMMAND_MEMORY )
> 
> But I should probably mention that I'm not 100% sure if this code base uses
> kernel coding style!

Hi Christian,

Thanks for taking a look at these patches! For better or for worse Xen
follows a different coding style from the Linux kernel (see CODING_STYLE
under xen.git).  In Xen we use:

    if ( rc != 0 ) 
    {
        return rc;
    }