On Tue, Sep 26, 2023 at 01:16:35AM -0700, Tian, Kevin wrote: > > From: Liu, Yi L <yi.l.liu@xxxxxxxxx> > > Sent: Thursday, September 21, 2023 3:51 PM > > > > From: Nicolin Chen <nicolinc@xxxxxxxxxx> > > > > Now enforce_cache_coherency and msi_cookie are kernel-managed hwpt > > things. > > So, they should be only setup on kernel-managed domains. If the attaching > > domain is a user-managed domain, redirect the hwpt to hwpt->parent to do > > it correctly. > > > > No redirection. The parent should already have the configuration done > when it's created. It shouldn't be triggered in the nesting path. iommufd_hw_pagetable_enforce_cc() is not only called in alloc(), but also in hwpt_attach/replace() if cc is not enforced by the alloc() because the idev that initiates the hwpt_alloc() might not have idev->enforce_cache_coherency. Only when another idev that has idev->enforce_cache_coherency attaches to the shared hwpt, the cc configuration would be done. In a nesting case encountering the same situation above, the S2 hwpt is allocated without the iommufd_hw_pagetable_enforce_cc(). But the 2nd idev that has idev->enforce_cache_coherency might attach directly to the S1 domain/hwpt without touching the S2 domain (for the same VM, S2 domain can be shared). In this case, without a redirection, the iommufd_hw_pagetable_enforce_cc() would be missed. Any thought? Nic
