Hi Jean, On 2/8/24 15:42, Jean-Philippe Brucker wrote: > 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. > For the series: > > Reviewed-by: Jean-Philippe Brucker <jean-phili...@linaro.org>
Thanks! and after reading your v2 last reply we case we need to support smaller aw ranges, I will do the change when the use case arises. Eric > >> 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/ >> >> 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 >>
