Thread (44 messages) 44 messages, 4 authors, 2021-03-31

Re: [PATCH 16/18] KVM: Don't take mmu_lock for range invalidation unless necessary

From: Paolo Bonzini <pbonzini@redhat.com>
Date: 2021-03-31 21:37:16
Also in: kvm, kvmarm, linux-mips, lkml

On 31/03/21 23:22, Sean Christopherson wrote:
On a related topic, any preference on whether to have an explicit "must_lock"
flag (what I posted), or derive the logic based on other params?

The helper I posted does:

	if (range->must_lock &&
	    kvm_mmu_lock_and_check_handler(kvm, range, &locked))
		goto out_unlock;

but it could be:

	if (!IS_KVM_NULL_FN(range->on_lock) && !range->may_block &&
	    kvm_mmu_lock_and_check_handler(kvm, range, &locked))
		goto out_unlock;

The generated code should be nearly identical on a modern compiler, so it's
purely a question of aesthetics.  I slightly prefer the explicit "must_lock" to
avoid spreading out the logic too much, but it also feels a bit superfluous.
I do as well, but I hope we don't need any lock after all as in the 
email I've just sent.

Paolo


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