On 05/07/2016 18:50, Nadav Amit wrote: > Paolo Bonzini <[email protected]> wrote: > >> >> >> On 05/07/2016 18:27, Nadav Amit wrote: >>>> Although such hardware is old, there are some hypervisors that do not set >>>> the ecap.coherency of emulated IOMMUs. Yes, it is unwise, but there is no >>>> reason to further punish these hypervisors. >> >> QEMU will need the kernel to respect ecap.coherency in order to support >> nested VFIO, for example. > > To clarify - the kernel respects the coherency, but performs more clflushes > than necessary. It has no functional impact, but induces performance > degradation (which I did not measure, but is likely to be several hundreds > of cycles per flush).
Oh, then QEMU indeed doesn't care about flushing the invalidation queue. Paolo _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
