On 22.10.24 19:01, Sean Christopherson wrote:
On Tue, Oct 22, 2024, Juergen Gross wrote:Testing whether to call kvm_tdp_page_fault() or vcpu->arch.mmu->page_fault() doesn't make sense, as kvm_tdp_page_fault() is selected only if vcpu->arch.mmu->page_fault == kvm_tdp_page_fault.It does when retpolines are enabled and significantly inflate the cost of the indirect call. This is a hot path in various scenarios, but KVM can't use static_call() to avoid the retpoline due to mmu->page_fault being a property of the current vCPU. Only kvm_tdp_page_fault() is special cased because all other mmu->page_fault targets are slow-ish and/or we don't care terribly about their performance.
Fair enough. :-) I'll modify the patch to add a comment in this regard in order to avoid similar simplification attempts in the future. Juergen
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