linux-kernel - Re: [patch V2 24/46] PCI: vmd: Mark VMD irqdomain with DOMAIN_BUS_VMD

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Message-ID: <20200930184755.GS816047@nvidia.com>
Date:   Wed, 30 Sep 2020 15:47:55 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     "Derrick, Jonathan" <jonathan.derrick@...el.com>
CC:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
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        "haiyangz@...rosoft.com" <haiyangz@...rosoft.com>,
        "Dey, Megha" <megha.dey@...el.com>,
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Subject: Re: [patch V2 24/46] PCI: vmd: Mark VMD irqdomain with
 DOMAIN_BUS_VMD_MSI

On Wed, Sep 30, 2020 at 01:08:27PM +0000, Derrick, Jonathan wrote:
> +Megha
> 
> On Wed, 2020-09-30 at 09:57 -0300, Jason Gunthorpe wrote:
> > On Wed, Sep 30, 2020 at 12:45:30PM +0000, Derrick, Jonathan wrote:
> > > Hi Jason
> > > 
> > > On Mon, 2020-08-31 at 11:39 -0300, Jason Gunthorpe wrote:
> > > > On Wed, Aug 26, 2020 at 01:16:52PM +0200, Thomas Gleixner wrote:
> > > > > From: Thomas Gleixner <tglx@...utronix.de>
> > > > > 
> > > > > Devices on the VMD bus use their own MSI irq domain, but it is not
> > > > > distinguishable from regular PCI/MSI irq domains. This is required
> > > > > to exclude VMD devices from getting the irq domain pointer set by
> > > > > interrupt remapping.
> > > > > 
> > > > > Override the default bus token.
> > > > > 
> > > > > Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> > > > > Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
> > > > >  drivers/pci/controller/vmd.c |    6 ++++++
> > > > >  1 file changed, 6 insertions(+)
> > > > > 
> > > > > +++ b/drivers/pci/controller/vmd.c
> > > > > @@ -579,6 +579,12 @@ static int vmd_enable_domain(struct vmd_
> > > > >  		return -ENODEV;
> > > > >  	}
> > > > >  
> > > > > +	/*
> > > > > +	 * Override the irq domain bus token so the domain can be distinguished
> > > > > +	 * from a regular PCI/MSI domain.
> > > > > +	 */
> > > > > +	irq_domain_update_bus_token(vmd->irq_domain, DOMAIN_BUS_VMD_MSI);
> > > > > +
> > > > 
> > > > Having the non-transparent-bridge hold a MSI table and
> > > > multiplex/de-multiplex IRQs looks like another good use case for
> > > > something close to pci_subdevice_msi_create_irq_domain()?
> > > > 
> > > > If each device could have its own internal MSI-X table programmed
> > > > properly things would work alot better. Disable capture/remap of the
> > > > MSI range in the NTB.
> > > We can disable the capture and remap in newer devices so we don't even
> > > need the irq domain.
> > 
> > You'd still need an irq domain, it just comes from
> > pci_subdevice_msi_create_irq_domain() instead of internal to this
> > driver.
> I have this set which disables remapping and bypasses the creation of
> the IRQ domain:
> https://patchwork.ozlabs.org/project/linux-pci/list/?series=192936

After Thomas's series VMD needs to supply a hierarchical IRQ domain to
get the correct PCI originator. This instead of the x86 patch in that
series. I think that domain should be created by
pci_subdevice_msi_create_irq_domain(), at least I'd start there.

Jason