On 1/18/22 12:45 PM, Pierre Morel wrote:
On 1/18/22 18:32, Matthew Rosato wrote:
On 1/18/22 12:20 PM, Pierre Morel wrote:
On 1/14/22 21:31, Matthew Rosato wrote:
This was previously removed as unnecessary; while that was true,
subsequent
changes will make KVM an additional required component for
vfio-pci-zdev.
Let's re-introduce CONFIG_VFIO_PCI_ZDEV as now there is actually a
reason
to say 'n' for it (when not planning to CONFIG_KVM).
Signed-off-by: Matthew Rosato <mjrosato@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 860424ccda1b..fedd1d4cb592 100644
--- a/drivers/vfio/pci/Kconfig
+++ b/drivers/vfio/pci/Kconfig
@@ -42,5 +42,16 @@ config VFIO_PCI_IGD
and LPC bridge config space.
To enable Intel IGD assignment through vfio-pci, say Y.
+
+config VFIO_PCI_ZDEV
+ 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.
In several patches we check on CONFIG_PCI (14,15,16,17 and 22) but we
may have PCI without VFIO_PCI, wouldn't it be a problem?
Here we define a new CONFIG entry and I have two questions:
1- there is no dependency on VFIO_PCI while the functionality is
obviously based on VFIO_PCI
It's not obvious from this diff, but this 'config VFIO_PCI_ZDEV'
statement is within an 'if VFIO_PCI' statement, just like VFIO_PCI_IGD
above -- so the dependency is there.
sorry, I remember now you already answered this to Christian last time.
2- Wouldn't it be possible to use this item and the single condition
for the different checks we need through the new VFIO interpretation
functionality.
Possibly, but 1) we'd have to make linking arch/s390/kvm/pci.o
dependent on CONFIG_VFIO_PCI instead of CONFIG_PCI in patch 14 and 2)
if the relationship between CONFIG_VFIO_PCI and CONFIG_PCI were to
ever change (though I don't see why it would..), we would be broken
because the symbols we are referencing really require CONFIG_PCI (as
they are located in s390 PCI).
Yes but VFIO_PCI_ZDEV depends on KVM, PCI and on VFIO_PCI
Wouldn't a single config item for this new code be easier to manage and
understand?
I guess my primary resistance is to abstracting/hiding the dependency.
Yes, userspace will never setup for zPCI interpretation without
CONFIG_VFIO_PCI{_ZDEV}, but that's not where the compilation dependency
is -- it's on CONFIG_PCI specifically.
But I guess on the other hand you could argue why even bother building
pci.o into kvm without CONFIG_VFIO_PCI_ZDEV as it will never be used.
OK, I will have a look at making this change. It will require a little
reorganization, at least moving this patch up before patch 14.
