On Sun, Feb 18, 2018 at 9:40 PM, Charles Gonçalves <[hidden email]> wrote:
> Im getting this Hypercall [op = 0x0040001a ] on xen trace but can't figure
> out which operation this is.
Bits in the higher part of EAX are normally "hypercall continuations".
This looks like an mmuext_op (0x1a == 26) that's been interrupted
part-way through and is resuming.
Xen doesn't have per-vcpu hypervisor stacks, so if it needs to
interrupt a hypercall, what it does is store information about how far
it got, then set the IP back one instruction. When the vcpu starts
again, it will re-execute the hypercall, and Xen will read the
"continuation" information and pick up again where it left off.