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([2001:b07:6468:f312:ec9b:111a:97e3:4baf]) by smtp.gmail.com with ESMTPSA id d2sm4665022wro.34.2020.09.25.17.40.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 25 Sep 2020 17:40:00 -0700 (PDT) Subject: Re: [PATCH 05/22] kvm: mmu: Add functions to handle changed TDP SPTEs To: Ben Gardon , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Cannon Matthews , Peter Xu , Sean Christopherson , Peter Shier , Peter Feiner , Junaid Shahid , Jim Mattson , Yulei Zhang , Wanpeng Li , Vitaly Kuznetsov , Xiao Guangrong References: <20200925212302.3979661-1-bgardon@google.com> <20200925212302.3979661-6-bgardon@google.com> From: Paolo Bonzini Message-ID: Date: Sat, 26 Sep 2020 02:39:59 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200925212302.3979661-6-bgardon@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 25/09/20 23:22, Ben Gardon wrote: > + > + /* > + * Recursively handle child PTs if the change removed a subtree from > + * the paging structure. > + */ > + if (was_present && !was_leaf && (pfn_changed || !is_present)) { > + pt = spte_to_child_pt(old_spte, level); > + > + for (i = 0; i < PT64_ENT_PER_PAGE; i++) { > + old_child_spte = *(pt + i); > + *(pt + i) = 0; > + handle_changed_spte(kvm, as_id, > + gfn + (i * KVM_PAGES_PER_HPAGE(level - 1)), > + old_child_spte, 0, level - 1); > + } Is it worth returning a "flush" value to the caller, to avoid multiple kvm_flush_remote_tlbs_with_address when e.g. zapping a 3rd-level PTE? Also I prefer if we already include here a "stupid" version of handle_changed_spte that just calls __handle_changed_spte. (If my suggestion is accepted, handle_changed_spte could actually handle the flushing). Paolo > + > + kvm_flush_remote_tlbs_with_address(kvm, gfn, > + KVM_PAGES_PER_HPAGE(level)); > + > + free_page((unsigned long)pt); > + }