On Wed, Feb 21, 2024 at 11:41:57AM +0100, Eric Auger wrote: > Hi, > > On 2/13/24 13:00, Michael S. Tsirkin wrote: > > On Tue, Feb 13, 2024 at 12:24:22PM +0100, Eric Auger wrote: > >> Hi Michael, > >> On 2/13/24 12:09, Michael S. Tsirkin wrote: > >>> On Tue, Feb 13, 2024 at 11:32:13AM +0100, Eric Auger wrote: > >>>> Do you have an other concern? > >>> I also worry a bit about migrating between hosts with different > >>> page sizes. Not with kvm I am guessing but with tcg it does work I think? > >> I have never tried but is it a valid use case? Adding Peter in CC. > >>> Is this just for vfio and vdpa? Can we limit this to these setups > >>> maybe? > >> I am afraid we know the actual use case too later. If the VFIO device is > >> hotplugged we have started working with 4kB granule. > >> > >> The other way is to introduce a min_granule option as done for aw-bits. > >> But it is heavier. > >> > >> Thanks > >> > >> Eric > > Let's say, if you are changing the default then we definitely want > > a way to get the cmpatible behaviour for tcg. > > So the compat machinery should be user-accessible too and documented. > > I guess I need to add a new option to guarantee the machine compat. > > I was thinking about an enum GranuleMode property taking the following > values, 4KB, 64KB, host > Jean, do you think there is a rationale offering something richer?
16KB seems to be gaining popularity, we should include that (I think it's the only granule supported by Apple IOMMU?). Hopefully that will be enough. Thanks, Jean > > Obviously being able to set the exact page_size_mask + host mode would > be better but this does not really fit into any std property type. > > Thanks > > Eric > > >
