On 3/5/18 11:03 am, David Gibson wrote: > On Wed, May 02, 2018 at 06:59:53PM +1000, Alexey Kardashevskiy wrote: >> On 2/5/18 4:37 pm, David Gibson wrote: >>> On Wed, May 02, 2018 at 02:45:57PM +1000, Alexey Kardashevskiy wrote: >>>> At the moment the PPC64/pseries guest only supports 4K/64K/16M IOMMU >>>> pages and POWER8 CPU supports the exact same set of page size so >>>> so far things worked fine. >>>> >>>> However POWER9 supports different set of sizes - 4K/64K/2M/1G and >>>> the last two - 2M and 1G - are not even allowed in the paravirt interface >>>> (RTAS DDW) so we always end up using 64K IOMMU pages, although we could >>>> back guest's 16MB IOMMU pages with 2MB pages on the host. >>>> >>>> This stores the supported host IOMMU page sizes in VFIOContainer and uses >>>> this later when creating a new DMA window. >>>> >>>> There should be no behavioral changes on platforms other than pseries. >>>> >>>> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru> >>> >>> What will happen if you try to use this on an older kernel without >>> your mismatching pagesize changes? >> >> I tried 1GB huge pages and "-global spapr-pci-host-bridge.pgsz=0x1011000" >> or 0x41011000. > > With a hash guest or a radix guest?
The guest was radix but how would it change anything? The guest can only ask for 4k/64k/16m for IOMMU. -- Alexey