KVM: x86: Allow userspace to set maximum VCPU id for VM

mainline inclusion
from mainline-v6.0-rc1
commit 35875316
category: feature
feature: IPI Virtualization
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I5ODSC
CVE: N/A
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=35875316384b71d23dc2a45a969732fc8cab16af



Intel-SIG: commit 35875316 ("KVM: x86: Allow userspace to set maximum VCPU id for VM")

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KVM: x86: Allow userspace to set maximum VCPU id for VM

Introduce new max_vcpu_ids in KVM for x86 architecture. Userspace
can assign maximum possible vcpu id for current VM session using
KVM_CAP_MAX_VCPU_ID of KVM_ENABLE_CAP ioctl().

This is done for x86 only because the sole use case is to guide
memory allocation for PID-pointer table, a structure needed to
enable VMX IPI.

By default, max_vcpu_ids set as KVM_MAX_VCPU_ID.

Suggested-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Zeng Guang <guang.zeng@intel.com>
Message-Id: <20220419154444.11888-1-guang.zeng@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Jason Zeng <jason.zeng@intel.com>

Signed-off-by: Jason Zeng <jason.zeng@intel.com>