Messages in this thread | | | Subject | Re: [PATCH RFC 00/15] Add VFIO mediated device support and IMS support for the idxd driver. | From | "Dey, Megha" <> | Date | Sun, 3 May 2020 15:31:39 -0700 |
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Hi Jason,
On 5/3/2020 3:22 PM, Jason Gunthorpe wrote: > On Fri, May 01, 2020 at 03:31:51PM -0700, Dey, Megha wrote: >>>> This has been my concern reviewing the implementation. IMS needs more >>>> than one in-tree user to validate degrees of freedom in the api. I had >>>> been missing a second "in-tree user" to validate the scope of the >>>> flexibility that was needed. >>> >>> IMS is too narrowly specified. >>> >>> All platforms that support MSI today can support IMS. It is simply a >>> way for the platform to give the driver an addr/data pair that triggers >>> an interrupt when a posted write is performed to that pair. >>> >> >> Well, yes and no. IMS requires interrupt remapping in addition to the >> dynamic nature of IRQ allocation. > > You've mentioned remapping a few times, but I really can't understand > why it has anything to do with platform_msi or IMS..
So after some internal discussions, we have concluded that IMS has no linkage with Interrupt remapping, IR is just a platform concept. IMS is just a name Intel came up with, all it really means is device managed addr/data writes to generate interrupts. Technically we can call something IMS even if device has its own location to store interrupts in non-pci standard mechanism, much like platform-msi indeed. We simply need to extend platform-msi to its address some of its shortcomings: increase number of interrupts to > 2048, enable dynamic allocation of interrupts, add mask/unmask callbacks in addition to write_msg etc. FWIW, even MSI can be IMS with rules on how to manage the addr/data writes following pci sig .. its just that.
I will be sending out an email shortly outlining the new design for IMS (A.K.A platform-msi part 2) and what are the improvements we want to add to the already existing platform-msi infrastructure.
Thank you so much for your comments, it helped us iron out some of these details :)
> > Jason >
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