[Xen-devel] [PATCH v3 11/11] docs: Describe PVHv2's VCPU hotplug procedure

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
CC: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
---
 docs/misc/hvmlite.markdown | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/docs/misc/hvmlite.markdown b/docs/misc/hvmlite.markdown
index 898b8ee..0045d22 100644
--- a/docs/misc/hvmlite.markdown
+++ b/docs/misc/hvmlite.markdown
@@ -75,3 +75,15 @@ info structure that's passed at boot time (field rsdp_paddr).
 
 Description of paravirtualized devices will come from XenStore, just as it's
 done for HVM guests.
+
+## VCPU hotplug ##
+
+VCPU hotplug (e.g. 'xl vcpu-set <domain> <num_vcpus>') for PVHv2 guests
+follows ACPI model where change in domain's number of VCPUS (stored in
+arch_domain.avail_vcpus) results in an SCI being sent to the guest. The
+guest then executes DSDT's PRSC method, updating MADT enable status for
+the affected VCPU.
+
+This is achieved by having the toolstack call XEN_DOMCTL_set_avail_vcpus
+which sets appropriate bits in ACPI GPE0 enable and status registers followed
+by sending VIRQ_SCI to the guest.
-- 
2.7.4


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