Hi Jean-Philippe, On Fri, 5 Mar 2021 09:30:49 +0100, Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx> wrote: > On Thu, Mar 04, 2021 at 09:46:03AM -0800, Jacob Pan wrote: > > Hi Jean-Philippe, > > > > On Thu, 4 Mar 2021 10:49:37 +0100, Jean-Philippe Brucker > > <jean-philippe@xxxxxxxxxx> wrote: > > > > > On Wed, Mar 03, 2021 at 04:02:05PM -0800, Jacob Pan wrote: > > > > Hi Jacob, > > > > > > > > On Wed, 3 Mar 2021 13:17:26 -0800, Jacob Pan > > > > <jacob.jun.pan@xxxxxxxxxxxxxxx> wrote: > > > > > > > > > Hi Tejun, > > > > > > > > > > On Wed, 3 Mar 2021 10:44:28 -0500, Tejun Heo <tj@xxxxxxxxxx> > > > > > wrote: > > > > > > On Sat, Feb 27, 2021 at 02:01:23PM -0800, Jacob Pan wrote: > > > > > > > IOASIDs are used to associate DMA requests with virtual > > > > > > > address spaces. They are a system-wide limited resource made > > > > > > > available to the userspace applications. Let it be VMs or > > > > > > > user-space device drivers. > > > > > > > > > > > > > > This RFC patch introduces a cgroup controller to address the > > > > > > > following problems: > > > > > > > 1. Some user applications exhaust all the available IOASIDs > > > > > > > thus depriving others of the same host. > > > > > > > 2. System admins need to provision VMs based on their needs > > > > > > > for IOASIDs, e.g. the number of VMs with assigned devices > > > > > > > that perform DMA requests with PASID. > > > > > > > > > > > > Please take a look at the proposed misc controller: > > > > > > > > > > > > http://lkml.kernel.org/r/20210302081705.1990283-2-vipinsh@xxxxxxxxxx > > > > > > > > > > > > Would that fit your bill? > > > > > The interface definitely can be reused. But IOASID has a different > > > > > behavior in terms of migration and ownership checking. I guess > > > > > SEV key IDs are not tied to a process whereas IOASIDs are. > > > > > Perhaps this can be solved by adding > > > > > + .can_attach = ioasids_can_attach, > > > > > + .cancel_attach = ioasids_cancel_attach, > > > > > Let me give it a try and come back. > > > > > > > > > While I am trying to fit the IOASIDs cgroup in to the misc cgroup > > > > proposal. I'd like to have a direction check on whether this idea of > > > > using cgroup for IOASID/PASID resource management is viable. > > > > > > Yes, even for host SVA it would be good to have a cgroup. Currently > > > the number of shared address spaces is naturally limited by number of > > > processes, which can be controlled with rlimit and cgroup. But on Arm > > > the hardware limit on shared address spaces is 64k (number of ASIDs), > > > easily exhausted with the default PASID and PID limits. So a cgroup > > > for managing this resource is more than welcome. > > > > > > It looks like your current implementation is very dependent on > > > IOASID_SET_TYPE_MM? I'll need to do more reading about cgroup to see > > > how easily it can be adapted to host SVA which uses > > > IOASID_SET_TYPE_NULL. > > Right, I was assuming have three use cases of IOASIDs: > > 1. host supervisor SVA (not a concern, just one init_mm to bind) > > 2. host user SVA, either one IOASID per process or perhaps some private > > IOASID for private address space > > 3. VM use for guest SVA, each IOASID is bound to a guest process > > > > My current cgroup proposal applies to #3 with IOASID_SET_TYPE_MM, which > > is allocated by the new /dev/ioasid interface. > > > > For #2, I was thinking you can limit the host process via PIDs cgroup? > > i.e. limit fork. > > That works but isn't perfect, because the hardware resource of shared > address spaces can be much lower that PID limit - 16k ASIDs on Arm. To > allow an admin to fairly distribute that resource we could introduce > another cgroup just to limit the number of shared address spaces, but > limiting the number of IOASIDs does the trick. > make sense. it would be cleaner to have a single approach to limit IOASIDs (as Jason asked). > > So the host IOASIDs are currently allocated from the system pool > > with quota of chosen by iommu_sva_init() in my patch, 0 means unlimited > > use whatever is available. https://lkml.org/lkml/2021/2/28/18 > > Yes that's sensible, but it would be good to plan the cgroup user > interface to work for #2 as well, even if we don't implement it right > away. > will do it in the next version. > Thanks, > Jean Thanks, Jacob
