Re: [PATCH v1 0/6] Check and sync host IOMMU cap/ecap with vIOMMU

[Jason Wang]

On Wed, Feb 28, 2024 at 5:46 PM Zhenzhong Duan <zhenzhong.duan@intel.com> wrote:
>
> Hi,
>
> Based on Joao's suggestion, the iommufd nesting prerequisite series [1]
> is further splitted to host IOMMU device abstract part [2] and vIOMMU
> check/sync part. This series implements the 2nd part.
>
> This enables vIOMMU to get host IOMMU cap/ecap information by implementing
> a new set/unset_iommu_device interface, then vIOMMU could check or sync
> with vIOMMU's own cap/ecap config.

Does it mean that it would supress the cap/ecap config from the qemu
command line? If yes, I wonder how to maintain the migration
compatibility.

Thanks

>
> It works by having device side, i.e. VFIO, register either an 
> IOMMULegacyDevice
> or IOMMUFDDevice to vIOMMU, which includes necessary data to archive that.
> Currently only VFIO device is supported, but it could also be used for other
> devices, i.e., VDPA.
>
> For coldplugged device, we can get its host IOMMU cap/ecap during qemu init,
> then check and sync into vIOMMU cap/ecap.
> For hotplugged device, vIOMMU cap/ecap is frozen, we could only check with
> vIOMMU cap/ecap, not allowed to update. If check fails, hotplugged will fail.
>
> This is also a prerequisite for incoming iommufd nesting series:
> 'intel_iommu: Enable stage-1 translation'.
>
> I didn't implement cap/ecap sync for legacy VFIO backend, would like to see
> what Eric want to put in IOMMULegacyDevice for virtio-iommu and if I can
> utilize some of them.
>
> Because it's becoming clear on community's suggestion, I'd like to remove
> rfc tag from this version.
>
> Qemu code can be found at:
> https://github.com/yiliu1765/qemu/tree/zhenzhong/iommufd_nesting_preq_part2_v1
>
> [1] 
> https://lore.kernel.org/qemu-devel/20240201072818.327930-1-zhenzhong.duan@intel.com
> [2] https://lists.gnu.org/archive/html/qemu-devel/2024-02/msg06314.html
>
> Thanks
> Zhenzhong
>
> Changelog:
> v1:
> - convert HostIOMMUDevice to sub object pointer in vtd_check_hdev
>
> rfcv2:
> - introduce common abstract HostIOMMUDevice and sub struct for different BEs 
> (Eric, Cédric)
> - remove iommufd_device.[ch] (Cédric)
> - remove duplicate iommufd/devid define from VFIODevice (Eric)
> - drop the p in aliased_pbus and aliased_pdevfn (Eric)
> - assert devfn and iommu_bus in pci_device_get_iommu_bus_devfn (Cédric, Eric)
> - use errp in iommufd_device_get_info (Eric)
> - split and simplify cap/ecap check/sync code in intel_iommu.c (Cédric)
> - move VTDHostIOMMUDevice declaration to intel_iommu_internal.h (Cédric)
> - make '(vtd->cap_reg >> 16) & 0x3fULL' a MACRO and add missed '+1' (Cédric)
> - block migration if vIOMMU cap/ecap updated based on host IOMMU cap/ecap
> - add R-B
>
>
> Yi Liu (2):
>   intel_iommu: Add set/unset_iommu_device callback
>   intel_iommu: Add a framework to check and sync host IOMMU cap/ecap
>
> Zhenzhong Duan (4):
>   intel_iommu: Extract out vtd_cap_init to initialize cap/ecap
>   intel_iommu: Implement check and sync mechanism in iommufd mode
>   intel_iommu: Use mgaw instead of s->aw_bits
>   intel_iommu: Block migration if cap is updated
>
>  hw/i386/intel_iommu_internal.h |   9 ++
>  include/hw/i386/intel_iommu.h  |   4 +
>  hw/i386/acpi-build.c           |   3 +-
>  hw/i386/intel_iommu.c          | 287 ++++++++++++++++++++++++++-------
>  4 files changed, 245 insertions(+), 58 deletions(-)
>
> --
> 2.34.1
>