Hi Eric/Alex, Thanks for your valuable suggestions and get back to you if anything is required. Thanks, Vikas On Fri, Sep 11, 2020 at 7:23 PM Auger Eric <eric.auger@xxxxxxxxxx> wrote: > > Hi Vikas, > > On 9/10/20 6:57 PM, Alex Williamson wrote: > > On Thu, 10 Sep 2020 16:15:27 +0530 > > Vikas Gupta <vikas.gupta@xxxxxxxxxxxx> wrote: > > > >> Hi Alex/Cornelia, > >> > >> We are looking for MSI interrupts for platform devices in user-space > >> applications via event/poll mechanism using VFIO. > >> > >> Since there is no support for MSI/MSIX handling in VFIO-platform in kernel, > >> it may not possible to get this feature in user-space. > >> > >> Is there any other way we can get this feature in user-space OR can you > >> please suggest if any patch or feature is in progress for same in VFIO > >> platform? > >> > >> Any suggestions would be helpful. > > > > Eric (Cc'd) is the maintainer of vfio-platform. > > > > vfio-platform devices don't have IRQ indexes dedicated to MSI and MSI-X > > like vfio-pci devices do (technically these are PCI concepts, but I > > assume we're referring generically to message signaled interrupts), but > > that's simply due to the lack of standardization in platform devices. > > Logically these are simply collections of edge triggered interrupts, > > which the vfio device API supports generically, it's simply a matter > > that the vfio bus driver exposing a vfio-platform device create an IRQ > > index exposing these vectors. Thanks, > > I have not worked on MSI support and I am not aware of any work > happening in this area. > > First I would recommend to look at IRQ related uapis exposed by VFIO: > VFIO_DEVICE_GET_IRQ_INFO > VFIO_DEVICE_SET_IRQS > > and try to understand if they can be implemented for MSIs in a generic > way in the vfio_platform driver using platform-msi helpers. > > For instance VFIO_DEVICE_GET_IRQ_INFO would need to return the number of > requested vectors. On init I guess we should allocate vectors using > platform_msi_domain_alloc_irqs/ devm_request_irq and in the handler > trigger the eventfd provided through VFIO_DEVICE_SET_IRQS. > > On userspace where you have to trap the MSI setup to call the above > functions and setup irqfd injection. This would be device specific as > opposed to PCI. That's just rough ideas at the moment. > > Thanks > > Eric > > > > > Alex > > >
