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KVM: X86: Yield to IPI target if necessary

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When sending a call-function IPI-many to vCPUs, yield if any of
the IPI target vCPUs was preempted, we just select the first
preempted target vCPU which we found since the state of target
vCPUs can change underneath and to avoid race conditions.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Wanpeng Li
2019-06-11 20:23:48 +08:00
committed by Paolo Bonzini
parent 11e349143e
commit f85f6e7bc9
4 changed files with 34 additions and 0 deletions
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11
Documentation/virtual/kvm/hypercalls.txt
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@@ -141,3 +141,14 @@ a0 corresponds to the APIC ID in the third argument (a2), bit 1
corresponds to the APIC ID a2+1, and so on.
Returns the number of CPUs to which the IPIs were delivered successfully.
7. KVM_HC_SCHED_YIELD
------------------------
Architecture: x86
Status: active
Purpose: Hypercall used to yield if the IPI target vCPU is preempted
a0: destination APIC ID
Usage example: When sending a call-function IPI-many to vCPUs, yield if
any of the IPI target vCPUs was preempted.