+4.143 KVM_MAP_MEMORY
+------------------------
+
+:Capability: KVM_CAP_MAP_MEMORY
+:Architectures: none
+:Type: vcpu ioctl
I think "vcpu ioctl" means theoretically it can be called on multiple vcpus.
What happens in that case?
Each vcpu can handle the ioctl simaltaneously.
Not sure whether it is implied, but should we document it can be called
simultaneously?
Also, I believe this is only supposed to be called before VM starts to
run? I think we should document that too.
This is userspace ABI, we need to be explicit on how it is supposed to
be called from userspace.
Btw, I believe there should be some justification in the changelog why
this should be a vcpu ioctl().
[...]
+:Parameters: struct kvm_memory_mapping(in/out)
+:Returns: 0 on success, <0 on error
+
+KVM_MAP_MEMORY populates guest memory without running vcpu.
+
+::
+
+ struct kvm_memory_mapping {
+ __u64 base_gfn;
+ __u64 nr_pages;
+ __u64 flags;
+ __u64 source;
+ };
+
+ /* For kvm_memory_mapping:: flags */
+ #define KVM_MEMORY_MAPPING_FLAG_WRITE _BITULL(0)
+ #define KVM_MEMORY_MAPPING_FLAG_EXEC _BITULL(1)
+ #define KVM_MEMORY_MAPPING_FLAG_USER _BITULL(2)
I am not sure what's the good of having "FLAG_USER"?
This ioctl is called from userspace, thus I think we can just treat this always
as user-fault?
The point is how to emulate kvm page fault as if vcpu caused the kvm page
fault. Not we call the ioctl as user context.
Sorry I don't quite follow. What's wrong if KVM just append the #PF
USER error bit before it calls into the fault handler?
My question is, since this is ABI, you have to tell how userspace is
supposed to use this. Maybe I am missing something, but I don't see how
USER should be used here.
