On Mon, 2020-11-30 at 18:41 +0000, Joao Martins wrote:
> int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
> {
> ...
> if (kvm_hv_hypercall_enabled(vcpu->kvm))
> return kvm_hv_hypercall(...);
>
> if (kvm_xen_hypercall_enabled(vcpu->kvm))
> return kvm_xen_hypercall(...);
> ...
> }
>
> And on kvm_xen_hypercall() for the cases VMM offloads to demarshal what the registers mean
> e.g. for event channel send 64-bit guest: RAX for opcode and RDI/RSI for cmd and port.
Right, although it's a little more abstract than that: "RDI/RSI for
arg#0, arg#1 respectively".
And those are RDI/RSI for 64-bit Xen, EBX/ECX for 32-bit Xen, and
RBX/RDI for Hyper-V. (And Hyper-V seems to use only the two, while Xen
theoretically has up to 6).
> The kernel logic wouldn't be much different at the core, so thought of tihs consolidation.
> But the added complexity would have come from having to deal with two userspace exit types
> -- indeed probably not worth the trouble as you pointed out.
Yeah, I think I'm just going to move the 'kvm_userspace_hypercall()'
from my patch to be 'kvm_xen_hypercall()' in a new xen.c but still
using KVM_EXIT_HYPERCALL. Then I can rebase your other patches on top
of that, with the evtchn bypass.
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