[PATCH v5 00/21] KVM: s390: enable zPCI for interpretive execution

Matthew Rosato
2022-04-04T21:28:07Z

Note: in this version, all IOMMU changes have been removed to be pursued
as a follow-on / in conjunction with IOMMUFD. This series proposes to
add only exploitation of the interpretive execution facilities.

Enable interpretive execution of zPCI instructions + adapter interruption
forwarding for s390x KVM vfio-pci. This is done by triggering a routine
when the VFIO group is associated with the KVM guest, transmitting to
firmware a special token (GISA designation) to enable that specific guest
for interpretive execution on that zPCI device. Load/store interpreation
enablement is then controlled by userspace (based upon whether or not a
SHM bit is placed in the virtual function handle). Adapter Event
Notification interpretation is controlled from userspace via a new KVM
ioctl.

By allowing intepretation of zPCI instructions and firmware delivery of
interrupts to guests, we can reduce the frequency of guest SIE exits for
zPCI.

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.

Changelog v4->v5:
- Remove all IOMMU changes - this series will continue to use vfio type1
for mapping; RPCIT enhancements will be pursued as a follow-on in
coordination with the IOMMUFD project
- Remove most of the ops from the proposed KVM ioctl -- combine the notion
of 'start' and 'enable interpretation' into a single operation that
occurs in response to assigning a KVM association to the VFIO group
- a new kvm ioctl is still being used to register/unregister for adapter
event notification forwarding. But teach it to use pin_user_pages
instead of gfn_to_page and perform accounting.
- Because we now attempt to enable interpretation for all devices (even
if the virtual PCI device has a SHM bit on) avoid setting the GISA for
the device and the ECB bits for the guest on hardware without SHM.
- found a bug with "s390/pci: stash associated GISA designation", namely
that CLP SET PCI FN (disable) expects the gisa designation to always be
0. Now that we set the gisa earlier, vfio-pci can trip this when
triggering restore for ISM.
- Add a single routine to determine if interpretation support is usable
on this host, to be used in multiple spots.
- eliminated arch/s390/include/asm/kvm_pci.h, moving most elements into
arch/s390/kvm/pci.h with one exception to asm/kvm_host.h

Matthew Rosato (21):
s390/sclp: detect the zPCI load/store interpretation facility
s390/sclp: detect the AISII facility
s390/sclp: detect the AENI facility
s390/sclp: detect the AISI facility
s390/airq: pass more TPI info to airq handlers
s390/airq: allow for airq structure that uses an input vector
s390/pci: externalize the SIC operation controls and routine
s390/pci: stash associated GISA designation
s390/pci: stash dtsm and maxstbl
KVM: s390: pci: add basic kvm_zdev structure
KVM: s390: pci: do initial setup for AEN interpretation
KVM: s390: pci: enable host forwarding of Adapter Event Notifications
KVM: s390: mechanism to enable guest zPCI Interpretation
KVM: s390: pci: provide routines for enabling/disabling interrupt
forwarding
KVM: s390: pci: add routines to start/stop interpretive execution
KVM: vfio: add s390x hook to register KVM guest designation
vfio-pci/zdev: add function handle to clp base capability
vfio-pci/zdev: different maxstbl for interpreted devices
KVM: s390: add KVM_S390_ZPCI_OP to manage guest zPCI devices
KVM: s390: introduce CPU feature for zPCI Interpretation
MAINTAINERS: additional files related kvm s390 pci passthrough

Documentation/virt/kvm/api.rst | 45 +++
MAINTAINERS | 1 +
arch/s390/include/asm/airq.h | 7 +-
arch/s390/include/asm/kvm_host.h | 16 +
arch/s390/include/asm/pci.h | 10 +
arch/s390/include/asm/pci_clp.h | 9 +-
arch/s390/include/asm/pci_insn.h | 29 +-
arch/s390/include/asm/sclp.h | 4 +
arch/s390/include/asm/tpi.h | 13 +
arch/s390/include/uapi/asm/kvm.h | 1 +
arch/s390/kvm/Makefile | 1 +
arch/s390/kvm/interrupt.c | 95 ++++-
arch/s390/kvm/kvm-s390.c | 81 +++-
arch/s390/kvm/kvm-s390.h | 10 +
arch/s390/kvm/pci.c | 666 +++++++++++++++++++++++++++++++
arch/s390/kvm/pci.h | 86 ++++
arch/s390/pci/pci.c | 15 +
arch/s390/pci/pci_clp.c | 7 +
arch/s390/pci/pci_insn.c | 4 +-
arch/s390/pci/pci_irq.c | 48 ++-
drivers/s390/char/sclp_early.c | 4 +
drivers/s390/cio/airq.c | 12 +-
drivers/s390/cio/qdio_thinint.c | 6 +-
drivers/s390/crypto/ap_bus.c | 9 +-
drivers/s390/virtio/virtio_ccw.c | 6 +-
drivers/vfio/pci/vfio_pci_zdev.c | 11 +-
include/uapi/linux/kvm.h | 31 ++
include/uapi/linux/vfio_zdev.h | 7 +
virt/kvm/vfio.c | 35 +-
29 files changed, 1216 insertions(+), 53 deletions(-)
create mode 100644 arch/s390/kvm/pci.c
create mode 100644 arch/s390/kvm/pci.h

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2.27.0