On Thu, Apr 01, 2021 at 10:23:55AM -0700, Jacob Pan wrote: > Hi Jason, > > On Wed, 31 Mar 2021 21:37:05 -0300, Jason Gunthorpe <jgg@xxxxxxxxxx> wrote: > > > On Wed, Mar 31, 2021 at 04:46:21PM -0700, Jacob Pan wrote: > > > Hi Jason, > > > > > > On Wed, 31 Mar 2021 09:38:01 -0300, Jason Gunthorpe <jgg@xxxxxxxxxx> > > > wrote: > > > > > > Get rid of the ioasid set. > > > > > > > > > > > > Each driver has its own list of allowed ioasids. > > > > [...] > > > > > > > > The /dev/ioasid FD replaces this security check. By becoming FD > > > > centric you don't need additional kernel security objects. > > > > > > > > Any process with access to the /dev/ioasid FD is allowed to control > > > > those PASID. The seperation between VMs falls naturally from the > > > > seperation of FDs without creating additional, complicated, security > > > > infrastrucure in the kernel. > > > > > > > > This is why all APIs must be FD focused, and you need to have a > > > > logical layering of responsibility. > > > > > > > > Allocate a /dev/ioasid FD > > > > Allocate PASIDs inside the FD > Just to be super clear. Do we allocate a FD for each PASID and return the > FD to the user? Or return the plain PASID number back to the user space? I would do multiple PASID's per /dev/ioasid FD because we expect alot of PASIDs to be in use and we'd run into FDno limits. > > > > Assign memory to the PASIDS > > > > > > > > Open a device FD, eg from VFIO or VDP > > > > Instruct the device FD to authorize the device to access PASID A in > > > > an ioasid FD > > > How do we know user provided PASID A was allocated by the ioasid FD? > > > > You pass in the ioasid FD and use a 'get pasid from fdno' API to > > extract the required kernel structure. > > > Seems you are talking about two FDs: > - /dev/ioasid FD No, just this one. > - per IOASID FD > This API ioasid = get_pasid_from_fd(dev_ioasid_fd, ioasid_fd); > dev_ioasid_fd will find the xarray for all the PASIDs allocated under it, > ioasid_fd wil be the index into the xarray to retrieve the actual ioasid. > Correct? 'ioasid_fd' is just the ioasid number in whatever numberspace the /dev/ioasid FD's use. > > Why only one? Each interaction with the other FDs should include the > > PASID/FD pair. There is no restriction to just one. > OK, one per subsystem-VM. For example, if a VM has a VFIO and a VDPA > device, it should only two /dev/ioasid FDs respectively. Correct? No, only one. For something like qemu's use case I mostly expect the vIOMMU driver will open /dev/ioasid for each vIOMMU instance it creates (basically only one) > > The act of programming the page tables and the act of authorizing a > > PCI BDF to use a PASID are distinct things with two different IOCTLs. > > > Why separate? Because they have different owners and different layers in the software. It is not about use case, it is about putting the control points where they naturally belong. > For a complex stack like vSVA, I feel we have to reduce moving parts and do > some divide and conquer. uAPI should have all come together with a user and user application. uAPI is hardest and most important part. Jason
