On Fri, 31 Oct 2025 10:50:04 +0000 Shameer Kolothum <[email protected]> wrote:
> From: Yi Liu <[email protected]> > > If user wants to expose PASID capability in vIOMMU, then VFIO would also > report the PASID cap for this device if the underlying hardware supports > it as well. > > As a start, this chooses to put the vPASID cap in the last 8 bytes of the > vconfig space. This is a choice in the good hope of no conflict with any > existing cap or hidden registers. For the devices that has hidden registers, > user should figure out a proper offset for the vPASID cap. This may require > an option for user to config it. Here we leave it as a future extension. > There are more discussions on the mechanism of finding the proper offset. > > https://lore.kernel.org/kvm/bn9pr11mb5276318969a212ad0649c7be8c...@bn9pr11mb5276.namprd11.prod.outlook.com/ > > Since we add a check to ensure the vIOMMU supports PASID, only devices > under those vIOMMUs can synthesize the vPASID capability. This gives > users control over which devices expose vPASID. > > Signed-off-by: Yi Liu <[email protected]> > Tested-by: Zhangfei Gao <[email protected]> > Signed-off-by: Shameer Kolothum <[email protected]> Whilst not particularly keen on this hack, I can't see a better solution. Reviewed-by: Jonathan Cameron <[email protected]>
