On Tue, Sep 30, 2014 at 8:48 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > On Tue, Sep 30, 2014 at 8:38 AM, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote: >> Maybe we should disable the IOMMU in 2.2, this is worth considering. >> > > Please do. > > Also, try booting this 2.2 QEMU candidate with nested virtualization > on. Then bind vfio to a virtio-pci device and watch the guest get > corrupted. QEMU will blame Linux for incorrectly programming the > hardware, and Linux will blame QEMU for its blatant violation of the > ACPI spec. Given that this is presumably most of the point of adding > IOMMU support, it seems like a terrible idea to let code like that > into the wild. > > If this happens, Linux may also end up needing a quirk to prevent vfio > from binding to QEMU 2.2's virtio-pci devices. I just confirmed that a guest with my patches blows up if I run it like this against QEMU master from today: PATH=.:$PATH virtme-run --kimg ~/apps/linux-devel/arch/x86/boot/bzImage -a intel_iommu=on --qemu-opts -machine q35,iommu=on IOW, QEMU master is indeed presenting an IOMMU that blows up the guest if the guest tries to use it as specified. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
