Re: [PATCH v4 00/32] KVM: s390: enable zPCI for interpretive execution

[Matthew Rosato <mjrosato@linux.ibm.com>]

On 3/14/22 3:44 PM, Matthew Rosato wrote:
> Note: A few patches in this series are dependent on Baolu's IOMMU domain ops
> split, which is currently in the next branch of linux-iommu. This series
> applies on top:
> https://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu.git
> 
> Enable interpretive execution of zPCI instructions + adapter interruption
> forwarding for s390x KVM vfio-pci.  This is done by introducing a new IOMMU
> domain for s390x (KVM-managed), indicating via vfio that this IOMMU domain
> should be used instead of the default, with subsequent management of the
> hardware assists being handled via a new KVM ioctl for zPCI management.
> 
> By allowing intepretation of zPCI instructions and firmware delivery of
> interrupts to guests, we can significantly reduce the frequency of guest
> SIE exits for zPCI.  We then see additional gains by handling a hot-path
> instruction that can still intercept to the hypervisor (RPCIT) directly
> in kvm via the new IOMMU domain, whose map operations update the host
> DMA table with pinned guest entries over the specified range.
> 
>  From the perspective of guest configuration, you passthrough zPCI devices
> in the same manner as before, with intepretation support being used by
> default if available in kernel+qemu.
> 
> Will reply with a link to the associated QEMU series.

QEMU series:
https://lore.kernel.org/kvm/20220314194920.58888-1-mjrosato@linux.ibm.com/