Il 20/05/2014 04:25, Jidong Xiao ha scritto:
Hi,
The structure kvm_segment is defined as follows:
struct kvm_segment {
__u64 base;
__u32 limit;
__u16 selector;
__u8 type;
__u8 present, dpl, db, s, l, g, avl;
__u8 unusable;
__u8 padding;
};
Since the VMX spec defines base is 64 bits, limit is 32bits, selector
is 16bits, understandably, __u64, __u32, __u16 is used for them
respectively.
However, the VMX spec defines that the access rights is 32bits, which
includes a 4 bits type, 2 bits dpl, and 1 bit for the
present,dpl,db,s,l,g,avl. So why here they are all defined as __u8? It
means that, each of them is represented by 8bits? This looks
inconsistent with the VMX spec.
This is not a VMX definition, it's part of the ioctl interface between
KVM and user-mode programs.
For the conversion code see vmx_get_segment and vmx_set_segment. These
should be never called in hot paths, except unfortunately when doing
nested virtualization.
Paolo
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