KVM: use cpu_relax when halt polling
SMT siblings share caches and other hardware, and busy halt polling will degrade its sibling performance if its sibling is working Sean Christopherson suggested as below: "Rather than disallowing halt-polling entirely, on x86 it should be sufficient to simply have the hardware thread yield to its sibling(s) via PAUSE. It probably won't get back all performance, but I would expect it to be close. This compiles on all KVM architectures, and AFAICT the intended usage of cpu_relax() is identical for all architectures." Suggested-by:Sean Christopherson <seanjc@google.com> Signed-off-by:
Li RongQing <lirongqing@baidu.com> Message-Id: <20210727111247.55510-1-lirongqing@baidu.com> Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com>
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