On Wed, Sep 14, 2022 at 06:18:18PM +0300, Kirill A. Shutemov wrote: > > > > > > > > > > The patch below implements something like this. It is PoC, build-tested only. > > > > > > > > > > To be honest, I hate it. It is clearly a layering violation. It feels > > > > > dirty. But I don't see any better way as we tie orthogonal features > > > > > together. > > > > > > > > > > Also I have no idea how to make forced PASID allocation if LAM enabled. > > > > > What the API has to look like? > > > > > > > > Jacob, Ashok, any comment on this part? > > > > > > > > I expect in many cases LAM will be enabled very early (like before malloc > > > > is functinal) in process start and it makes PASID allocation always fail. > > > > > > > > Any way out? > > > > > > We need closure on this to proceed. Any clue? > > > > Failing PASID allocation seems like the right thing to do here. If the > > application is explicitly allocating PASID's it can opt-out using the > > similar mechanism you have for LAM enabling. So user takes > > responsibility for sanitizing pointers. > > > > If some library is using an accelerator without application knowledge, > > that would use the failure as a mechanism to use an alternate path if > > one exists. > > > > I don't know if both LAM and SVM need a separate forced opt-in (or i > > don't have an opinion rather). Is this what you were asking? > > > > + Joerg, JasonG in case they have an opinion. > > My point is that the patch provides a way to override LAM vs. PASID mutual > exclusion, but only if PASID allocated first. If we enabled LAM before > PASID is allcoated there's no way to forcefully allocate PASID, bypassing > LAM check. I think there should be one, no? Yes, we should have one for force enabling SVM too if the application asks for forgiveness.
