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KVM: x86: reduce pvclock_gtod_sync_lock critical sections

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There is no need to include changes to vcpu->requests into
the pvclock_gtod_sync_lock critical section.  The changes to
the shared data structures (in pvclock_update_vm_gtod_copy)
already occur under the lock.

Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2021-03-25 14:05:11 -04:00
parent 6ebae23c07
commit c2c647f91a
1 changed files with 4 additions and 6 deletions
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10
arch/x86/kvm/x86.c
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@ -2561,10 +2561,12 @@ static void kvm_gen_update_masterclock(struct kvm *kvm)
kvm_hv_invalidate_tsc_page(kvm);
spin_lock(&ka->pvclock_gtod_sync_lock);
kvm_make_mclock_inprogress_request(kvm);
/* no guest entries from this point */
spin_lock(&ka->pvclock_gtod_sync_lock);
pvclock_update_vm_gtod_copy(kvm);
spin_unlock(&ka->pvclock_gtod_sync_lock);
kvm_for_each_vcpu(i, vcpu, kvm)
kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
@ -2572,8 +2574,6 @@ static void kvm_gen_update_masterclock(struct kvm *kvm)
/* guest entries allowed */
kvm_for_each_vcpu(i, vcpu, kvm)
kvm_clear_request(KVM_REQ_MCLOCK_INPROGRESS, vcpu);
spin_unlock(&ka->pvclock_gtod_sync_lock);
#endif
}
@ -7739,16 +7739,14 @@ static void kvm_hyperv_tsc_notifier(void)
struct kvm_arch *ka = &kvm->arch;
spin_lock(&ka->pvclock_gtod_sync_lock);
pvclock_update_vm_gtod_copy(kvm);
spin_unlock(&ka->pvclock_gtod_sync_lock);
kvm_for_each_vcpu(cpu, vcpu, kvm)
kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
kvm_for_each_vcpu(cpu, vcpu, kvm)
kvm_clear_request(KVM_REQ_MCLOCK_INPROGRESS, vcpu);
spin_unlock(&ka->pvclock_gtod_sync_lock);
}
mutex_unlock(&kvm_lock);
}