Messages in this thread | | | Subject | Re: [Xen-devel] [PATCH linux 3/8] x86/xen: use xen_vcpu_id mapping for HYPERVISOR_vcpu_op | From | David Vrabel <> | Date | Wed, 29 Jun 2016 13:26:24 +0100 |
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On 28/06/16 17:47, Vitaly Kuznetsov wrote: > HYPERVISOR_vcpu_op passes Linux's idea of vCPU id as a parameter while > Xen's idea is expected. In some cases these ideas diverge so we need to > do remapping. > > There is an issue, however. PV guests do VCPUOP_is_up very early > (see xen_fill_possible_map() and xen_filter_cpu_maps()) when we don't have > perpu areas initialized. While it could be solved with switching to > early_percpu for xen_vcpu_id I think it's not worth it: PV guests will > probably never get to the point where their idea of vCPU id diverges from > Xen's. [...] > static inline int > HYPERVISOR_vcpu_op(int cmd, int vcpuid, void *extra_args) > { > - return _hypercall3(int, vcpu_op, cmd, vcpuid, extra_args); > + /* > + * PV guests call HYPERVISOR_vcpu_op before percpu areas are > + * initialized. As we always use direct mapping for vCPU ids > + * for them we can simply use Linux vcpuid here. > + */ > + return _hypercall3(int, vcpu_op, cmd, > + per_cpu(xen_vcpu_id, vcpuid) != -1 ? > + per_cpu(xen_vcpu_id, vcpuid) : vcpuid, > + extra_args); > }
HYPERVISOR_vcpu_op() should take Xen VCPUs, with the callers doing the mapping.
David
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