On 05/16/2011 02:11 AM, Nadav Har'El wrote:
On Thu, May 12, 2011, Avi Kivity wrote about "Re: [PATCH 0/30] nVMX: Nested VMX, v9": > Ah, yes. For live migration to work, all vmcb state must be accessible > via vendor-independent accessors once an exit is completely handled. > For example, GPRs are accessible via kvm_register_read(), and without > nesting, interrupt state is stowed in the interrupt queue, but if you > keep IDT_VECTORING_INFO live between exit and entry, you can lose it if > you migrate at this point. Hi, I can quite easily save this state in a different place which is saved - The easiest will just be to use vmcs12, which has place for exactly the fields we want to save (and they are rewritten anyway when we exit to L1).
You would still need ->valid_idt_vectoring_info to know you need special handling, no?
Avi, would you you like me use this sort of solution to avoid the extra state? Of course, considering that anyway, live migration with nested VMX probably still doesn't work for a dozen other reasons :( Or do you consider this not enough, and rather that it is necessary that nested VMX should use exactly the same logic as nested SVM does - namely, use tricks like SVM's "exit_required" instead of our different tricks?
I think svm is rather simple here using svm_complete_interrupts() to decode exit_int_info into the arch independent structures. I don't think ->exit_required is a hack - it could probably be improved but I think it does the right thing essentially. For example svm_nmi_allowed() will return true if in guest mode and NMI interception is enabled.
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