Messages in this thread | | | Date | Thu, 20 Jan 2022 11:38:29 +0100 | Subject | Re: [RFC PATCH v1 06/10] KVM: s390: Add vm IOCTL for key checked guest absolute memory access | From | Thomas Huth <> |
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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
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