Messages in this thread | | | Subject | Re: [RFC PATCH] pci: add pci_irq_get_affinity_vector() | From | Hannes Reinecke <> | Date | Tue, 8 Nov 2016 16:08:51 +0100 |
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On 11/08/2016 03:56 PM, Christoph Hellwig wrote: > On Tue, Nov 08, 2016 at 08:47:21AM +0100, Hannes Reinecke wrote: >> Add a reverse-mapping function to return the interrupt vector for >> any CPU if interrupt affinity is enabled. > > What's the use case of it? > > Also as-is this won't work due to the non-affinity vectors that > have the affinity set to all cpus. It will get even worse if we have > to support things like virtio_net that have multiple interrupts per > CPU due to the send and receive virtqueues. > The use-case here is that one needs to feed the MSI-X index into the driver command structure. While we can extract that number trivially with scsi-mq, but for scsi-sq we don't have such means.
So if we start assigning interrupt affinity per default we need to figure out the msi-x index from a given SCSI command. Currently most of these drivers keep an internal CPU map which I'd love to get rid of. Hence this patch.
And before you complain: Yes, this patch is wrong; it returns the vector and not the index (which is what I'm after). I found that on my test machine :-(
The main impetus of this RFC is to figure out if such a function would have a chance of getting upstream, or if I have to continue use cpumaps in the drivers.
Cheers,
Hannes -- Dr. Hannes Reinecke Teamlead Storage & Networking hare@suse.de +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg)
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