Nadav Amit <nadav.a...@gmail.com> wrote: > Joerg Roedel <j...@8bytes.org> wrote: > >> On Fri, Jun 24, 2016 at 06:13:14AM -0700, Nadav Amit wrote: >>> According to the manual: "Hardware access to ... invalidation queue ... >>> are always coherent." >>> >>> Remove unnecassary clflushes accordingly. >> >> It is one thing what the spec says and another how hardware really >> behaves. Have you tested this on (potentially really old) VT-d machines >> to make sure the spec is _always_ right here? > > No I didn’t as the commit message says. I would be happy for someones’ > tested-by. > > Having said that - FreeBSD does not do these (unnecessary) > invalidations [1], and their code comment clearly says it. Since this code > is not new, I would assume FreeBSD would crash by now if the code was > buggy. > > 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.
Ping? To clarify - this behavior applies to the guest of VMware and KVM (which uses QEMU for IOMMU emulation). Regardless, please respond to the other patch I sent as well. Thanks, Nadav _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
