On 18/01/2022 10.52, Janis Schoetterl-Glausch wrote:
Channel I/O honors storage keys and is performed on absolute memory.
For I/O emulation user space therefore needs to be able to do key
checked accesses.
The vm IOCTL supports read/write accesses, as well as checking
if an access would succeed.
...
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index e3f450b2f346..dd04170287fd 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -572,6 +572,8 @@ struct kvm_s390_mem_op {
#define KVM_S390_MEMOP_LOGICAL_WRITE 1
#define KVM_S390_MEMOP_SIDA_READ 2
#define KVM_S390_MEMOP_SIDA_WRITE 3
+#define KVM_S390_MEMOP_ABSOLUTE_READ 4
+#define KVM_S390_MEMOP_ABSOLUTE_WRITE 5
Not quite sure about this - maybe it is, but at least I'd like to see this
discussed: Do we really want to re-use the same ioctl layout for both, the
VM and the VCPU file handles? Where the userspace developer has to know that
the *_ABSOLUTE_* ops only work with VM handles, and the others only work
with the VCPU handles? A CPU can also address absolute memory, so why not
adding the *_ABSOLUTE_* ops there, too? And if we'd do that, wouldn't it be
sufficient to have the VCPU ioctls only - or do you want to call these
ioctls from spots in QEMU where you do not have a VCPU handle available?
(I/O instructions are triggered from a CPU, so I'd assume that you should
have a VCPU handle around?)
Thomas
