Re: [Xen-devel] [PATCH] x86: move vgc_flags to struct pv_vcpu

[Jan Beulich <jbeulich@xxxxxxxx>]

On 03.01.2020 12:19, Julien Grall wrote:
> How do you manage secondary CPUs on HVM/PVH guest?

Secondary CPUs have architectural state they start with, and
there's very little control an OS has over initial register
state: There's just an 8-bit value specifying (part of) the
address the CPU should start executing from. All other
registers get set to hard coded values. And that 8-bit value
is part of the IPI message the primary CPU sends to the AP
to be brought up (i.e. there's no hypercall involved here).

For PVH, a variant of the normal PV model of starting vCPU-s
gets used, i.e. via VCPUOP_initialise.

Jan

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