Messages in this thread | | | Date | Tue, 30 Nov 2021 17:16:29 +0100 | Subject | Re: [PATCH 27/28] KVM: x86/mmu: Do remote TLB flush before dropping RCU in TDP MMU resched | From | Paolo Bonzini <> |
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On 11/30/21 16:45, Sean Christopherson wrote: >> Couldn't this sleep in kvm_make_all_cpus_request, whilst in an RCU read-side >> critical section? > No. And if kvm_make_all_cpus_request() can sleep, the TDP MMU is completely hosed > as tdp_mmu_zap_spte_atomic() and handle_removed_tdp_mmu_page() currently call > kvm_flush_remote_tlbs_with_range() while under RCU protection. > > kvm_make_all_cpus_request_except() disables preemption via get_cpu(), and > smp_call_function() doubles down on disabling preemption as the inner helpers > require preemption to be disabled, so anything below them should complain if > there's a might_sleep(). hv_remote_flush_tlb_with_range() takes a spinlock, so > nothing in there should be sleeping either.
Yeah, of course you're right.
Paolo
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