Re: [Xen-users] Getting Hypercall [op = 0x0040001a ] on trace

[George Dunlap <dunlapg@xxxxxxxxx>]

On Sun, Feb 18, 2018 at 9:40 PM, Charles Gonçalves <charles.fg@xxxxxxxxx> wrote:
> Hello,
>
> 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.

 -George

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