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([2001:b07:6468:f312:75e3:aaa7:77d6:f4e4]) by smtp.gmail.com with ESMTPSA id d18sm1146388wrm.10.2020.09.29.23.28.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 29 Sep 2020 23:28:27 -0700 (PDT) Subject: Re: [PATCH 07/22] kvm: mmu: Support zapping SPTEs in the TDP MMU To: Sean Christopherson , Ben Gardon Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Cannon Matthews , Peter Xu , Peter Shier , Peter Feiner , Junaid Shahid , Jim Mattson , Yulei Zhang , Wanpeng Li , Vitaly Kuznetsov , Xiao Guangrong References: <20200925212302.3979661-1-bgardon@google.com> <20200925212302.3979661-8-bgardon@google.com> <20200930061533.GC29659@linux.intel.com> From: Paolo Bonzini Message-ID: <40a793f9-c58f-7b0e-5835-d83eed9f6ba0@redhat.com> Date: Wed, 30 Sep 2020 08:28:26 +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: <20200930061533.GC29659@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/09/20 08:15, Sean Christopherson wrote: >> kvm_zap_obsolete_pages(kvm); >> + >> + if (kvm->arch.tdp_mmu_enabled) >> + kvm_tdp_mmu_zap_all(kvm); > > Haven't looked into how this works; is kvm_tdp_mmu_zap_all() additive to > what is done by the legacy zapping, or is it a replacement? It's additive because the shadow MMU is still used for nesting. >> + >> spin_unlock(&kvm->mmu_lock); >> } >> @@ -57,8 +58,13 @@ bool is_tdp_mmu_root(struct kvm *kvm, hpa_t hpa) >> return root->tdp_mmu_page; >> } >> >> +static bool zap_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root, >> + gfn_t start, gfn_t end); >> + >> static void free_tdp_mmu_root(struct kvm *kvm, struct kvm_mmu_page *root) >> { >> + gfn_t max_gfn = 1ULL << (boot_cpu_data.x86_phys_bits - PAGE_SHIFT); > > BIT_ULL(...) Not sure about that. Here the point is not to have a single bit, but to do a power of two. Same for the version below. >> + * If the MMU lock is contended or this thread needs to yield, flushes >> + * the TLBs, releases, the MMU lock, yields, reacquires the MMU lock, >> + * restarts the tdp_iter's walk from the root, and returns true. >> + * If no yield is needed, returns false. >> + */ >> +static bool tdp_mmu_iter_cond_resched(struct kvm *kvm, struct tdp_iter *iter) >> +{ >> + if (need_resched() || spin_needbreak(&kvm->mmu_lock)) { >> + kvm_flush_remote_tlbs(kvm); >> + cond_resched_lock(&kvm->mmu_lock); >> + tdp_iter_refresh_walk(iter); >> + return true; >> + } else { >> + return false; >> + } > > Kernel style is to not bother with an "else" if the "if" returns. I have rewritten all of this in my version anyway. :) Paolo