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kvm: introduce KVM_MAX_VCPU_ID

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The KVM_MAX_VCPUS define provides the maximum number of vCPUs per guest, and
also the upper limit for vCPU ids. This is okay for all archs except PowerPC
which can have higher ids, depending on the cpu/core/thread topology. In the
worst case (single threaded guest, host with 8 threads per core), it limits
the maximum number of vCPUS to KVM_MAX_VCPUS / 8.

This patch separates the vCPU numbering from the total number of vCPUs, with
the introduction of KVM_MAX_VCPU_ID, as the maximal valid value for vCPU ids
plus one.

The corresponding KVM_CAP_MAX_VCPU_ID allows userspace to validate vCPU ids
before passing them to KVM_CREATE_VCPU.

This patch only implements KVM_MAX_VCPU_ID with a specific value for PowerPC.
Other archs continue to return KVM_MAX_VCPUS instead.

Suggested-by: Radim Krcmar <rkrcmar@redhat.com>
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Greg Kurz
2016-05-09 18:13:37 +02:00
committed by Paolo Bonzini
parent 9b9e3fc4d5
commit 0b1b1dfd52
5 changed files with 19 additions and 3 deletions
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1
include/uapi/linux/kvm.h
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@@ -865,6 +865,7 @@ struct kvm_ppc_smmu_info {
#define KVM_CAP_SPAPR_TCE_64 125
#define KVM_CAP_ARM_PMU_V3 126
#define KVM_CAP_VCPU_ATTRIBUTES 127
#define KVM_CAP_MAX_VCPU_ID 128
#ifdef KVM_CAP_IRQ_ROUTING