On Thu, Feb 08, 2024 at 11:10:16AM +0100, Eric Auger wrote: > In [1] and [2] we attempted to fix a case where a VFIO-PCI device > protected with a virtio-iommu is assigned to an x86 guest. On x86 > the physical IOMMU may have an address width (gaw) of 39 or 48 bits > whereas the virtio-iommu exposes a 64b input address space by default. > Hence the guest may try to use the full 64b space and DMA MAP > failures may be encountered. To work around this issue we endeavoured > to pass usable host IOVA regions (excluding the out of range space) from > VFIO to the virtio-iommu device so that the virtio-iommu driver can > query those latter during the probe request and let the guest iommu > kernel subsystem carve them out. > > However if there are several devices in the same iommu group, > only the reserved regions of the first one are taken into > account by the iommu subsystem of the guest. This generally > works on baremetal because devices are not going to > expose different reserved regions. However in our case, this > may prevent from taking into account the host iommu geometry. > > So the simplest solution to this problem looks to introduce an > input address width option, aw-bits, which matches what is > done on the intel-iommu. By default, from now on it is set > to 39 bits with pc_q35 and 48 with arm virt. This replaces the > previous default value of 64b. So we need to introduce a compat > for machines older than 9.0 to behave similarly. We use > hw_compat_8_2 to acheive that goal. > > Outstanding series [2] remains useful to let resv regions beeing > communicated on time before the probe request. > > [1] [PATCH v4 00/12] VIRTIO-IOMMU/VFIO: Don't assume 64b IOVA space > https://lore.kernel.org/all/20231019134651.842175-1-eric.au...@redhat.com/ > - This is merged - > > [2] [RFC 0/7] VIRTIO-IOMMU/VFIO: Fix host iommu geometry handling for > hotplugged devices > https://lore.kernel.org/all/20240117080414.316890-1-eric.au...@redhat.com/ > - This is pending for review on the ML - > > This series can be found at: > https://github.com/eauger/qemu/tree/virtio-iommu-aw-bits-v3 > previous > https://github.com/eauger/qemu/tree/virtio-iommu-aw-bits-v2 > > Applied on top of [3] > [PATCH v2] virtio-iommu: Use qemu_real_host_page_mask as default > page_size_mask > https://lore.kernel.org/all/20240117132039.332273-1-eric.au...@redhat.com/
So, I applied this without that patch until we agree whether there are compat issues in that one. Seems to work without or did I miss anything? > History: > v2 -> v3: > - Collected Zhenzhong and Cédric's R-b + Yanghang's T-b > - use &error_abort instead of NULL error handle > on object_property_get_uint() call (Cédric) > - use VTD_HOST_AW_39BIT (Cédric) > > v1 -> v2 > - Limit aw to 48b on ARM > - Check aw is within [32,64] > - Use hw_compat_8_2 > > > Eric Auger (3): > virtio-iommu: Add an option to define the input range width > virtio-iommu: Trace domain range limits as unsigned int > hw: Set virtio-iommu aw-bits default value on pc_q35 and arm virt > > include/hw/virtio/virtio-iommu.h | 1 + > hw/arm/virt.c | 6 ++++++ > hw/core/machine.c | 5 ++++- > hw/i386/pc.c | 6 ++++++ > hw/virtio/virtio-iommu.c | 7 ++++++- > hw/virtio/trace-events | 2 +- > 6 files changed, 24 insertions(+), 3 deletions(-) > > -- > 2.41.0