Getting Hypercall [op = 0x0040001a ] on trace

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Getting Hypercall [op = 0x0040001a ] on trace

Charles Gonçalves
Hello, 

Im getting this Hypercall [op = 0x0040001a ] on xen trace  but can't figure out which operation this is.

Using old Xen 4.4.1.
Looking at documentation  and also using grep into source code couldn't figure out which hypercall this is.

Can someone help clarify this?
--
Atenciosamente, 
Charles F.'. Gonçalves

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

George Dunlap
On Sun, Feb 18, 2018 at 9:40 PM, Charles Gonçalves <[hidden email]> 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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