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KVM: x86: Optimize kvm->lock and SRCU interaction (KVM_X86_SET_MSR_FILTER)

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Reduce time spent holding kvm->lock: unlock mutex before calling
synchronize_srcu().  There is no need to hold kvm->lock until all vCPUs
have been kicked, KVM only needs to guarantee that all vCPUs will switch
to the new filter before exiting to userspace.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
Link: https://lore.kernel.org/r/20230107001256.2365304-3-mhal@rbox.co
[sean: expand changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Michal Luczaj
2023-01-07 01:12:52 +01:00
committed by Sean Christopherson
parent 95744a90db
commit 708f799d22
1 changed files with 1 additions and 1 deletions
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arch/x86/kvm/x86.c
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@@ -6497,12 +6497,12 @@ static int kvm_vm_ioctl_set_msr_filter(struct kvm *kvm,
old_filter = srcu_dereference_check(kvm->arch.msr_filter, &kvm->srcu, 1);
rcu_assign_pointer(kvm->arch.msr_filter, new_filter);
mutex_unlock(&kvm->lock);
synchronize_srcu(&kvm->srcu);
kvm_free_msr_filter(old_filter);
kvm_make_all_cpus_request(kvm, KVM_REQ_MSR_FILTER_CHANGED);
mutex_unlock(&kvm->lock);
return 0;
}