On 14/06/2022 10.56, Pierre Morel wrote:
On 6/8/22 15:15, Matthew Rosato wrote:
On 6/8/22 2:19 AM, Thomas Huth wrote:
On 06/06/2022 22.33, Matthew Rosato wrote:
The current contents of vfio-pci-zdev are today only useful in a KVM
environment; let's tie everything currently under vfio-pci-zdev to
this Kconfig statement and require KVM in this case, reducing complexity
(e.g. symbol lookups).
Signed-off-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
Reviewed-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
drivers/vfio/pci/Kconfig | 11 +++++++++++
drivers/vfio/pci/Makefile | 2 +-
include/linux/vfio_pci_core.h | 2 +-
3 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
index 4da1914425e1..f9d0c908e738 100644
--- a/drivers/vfio/pci/Kconfig
+++ b/drivers/vfio/pci/Kconfig
@@ -44,6 +44,17 @@ config VFIO_PCI_IGD
To enable Intel IGD assignment through vfio-pci, say Y.
endif
+config VFIO_PCI_ZDEV_KVM
+ bool "VFIO PCI extensions for s390x KVM passthrough"
+ depends on S390 && KVM
+ default y
+ help
+ Support s390x-specific extensions to enable support for enhancements
+ to KVM passthrough capabilities, such as interpretive execution of
+ zPCI instructions.
+
+ To enable s390x KVM vfio-pci extensions, say Y.
Is it still possible to disable CONFIG_VFIO_PCI_ZDEV_KVM ? Looking at the
later patches (e.g. 20/21 where you call kvm_s390_pci_zpci_op() from
kvm-s390.c), it rather seems to me that it currently cannot be disabled
independently (as long as KVM is enabled).
Yes, you can build with, for example, CONFIG_VFIO_PCI_ZDEV_KVM=n and
CONFIG_KVM=m -- I tested it again just now. The result is kvm and
vfio-pci are built and vfio-pci works, but none of the vfio-pci-zdev
extensions are available (including zPCI interpretation).
This is accomplished via the placement of some IS_ENABLED checks. Some
calls (e.g. AEN init) are fenced by IS_ENABLED(CONFIG_VFIO_PCI_ZDEV_KVM).
There are also some areas that are fenced off via a call to
kvm_s390_pci_interp_allowed() which also includes an IS_ENABLED check
along with checks for facility and cpu id.
Using patch 20 as an example, KVM_CAP_S390_ZPCI_OP will always be reported
as unavailable to userspace if CONFIG_VFIO_PCI_ZDEV_KVM=n due to the call
to kvm_s390_pci_interp_allowed(). If userspace sends us the ioctl anyway,
we will return -EINVAL because there is again a
IS_ENABLED(CONFIG_VFIO_PCI_ZDEV_KVM) check before we read the ioctl args
from userspace.
Yes and the code will not be generated by the compiler in patch 20 after the
break if CONFIG_VFIO_PCI_ZDEV_KVM is not enabled.
+ case KVM_S390_ZPCI_OP: {
+ struct kvm_s390_zpci_op args;
+
+ r = -EINVAL;
+ if (!IS_ENABLED(CONFIG_VFIO_PCI_ZDEV_KVM))
+ break;
Code not generated----v
+ if (copy_from_user(&args, argp, sizeof(args))) {
+ r = -EFAULT;
+ break;
+ }
+ r = kvm_s390_pci_zpci_op(kvm, &args);
+ break;
----------^
OK, good to know, thanks for the clarification!
Thomas
