Hi, On Mon, May 04, 2020 at 07:54:03PM +0530, Prabhakar Kushwaha wrote: > Dear Jean, > > On Thu, Apr 30, 2020 at 8:11 PM Jean-Philippe Brucker > <jean-philippe@xxxxxxxxxx> wrote: > > > > If the SMMU supports it and the kernel was built with HTTU support, enable > > is there any framework/config for HTTU which must be enabled to use this patch? > > > > We can enable HTTU even if CPUs don't support it, because the kernel > > always checks for HW dirty bit and updates the PTE flags atomically. > > > I believe, this statement is valid in context of this patch-set only. > > One cannot use code snipped to test HTTU because exiting > io-pgtable-arm.c driver doesn't have framework to leverage HTTU > benfits. It by-default sets AF=1 and does not set DBM. Right, this patch only sets the hardware access and dirty flags for SVA (page tables shared with the CPU through iommu_bind*()), it doesn't enable anything for iommu_map/unmap(). Although I remember discussing it for VM migration, I don't know of any effort to use hardware access/dirty bits outside of SVA. Thanks, Jean
