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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id gu2sm993259ejb.96.2021.08.12.09.18.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Aug 2021 09:18:25 -0700 (PDT) To: Sean Christopherson Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Ben Gardon References: <20210812050717.3176478-1-seanjc@google.com> <20210812050717.3176478-2-seanjc@google.com> From: Paolo Bonzini Subject: Re: [PATCH 1/2] KVM: x86/mmu: Don't skip non-leaf SPTEs when zapping all SPTEs Message-ID: <01b22936-49b0-638e-baf8-269ba93facd8@redhat.com> Date: Thu, 12 Aug 2021 18:18:24 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210812050717.3176478-2-seanjc@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/08/21 07:07, Sean Christopherson wrote: > @@ -739,8 +749,16 @@ static bool zap_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root, > gfn_t start, gfn_t end, bool can_yield, bool flush, > bool shared) > { > + bool zap_all = (end == ZAP_ALL_END); > struct tdp_iter iter; > > + /* > + * Bound the walk at host.MAXPHYADDR, guest accesses beyond that will > + * hit a #PF(RSVD) and never get to an EPT Violation/Misconfig / #NPF, > + * and so KVM will never install a SPTE for such addresses. > + */ > + end = min(end, 1ULL << (shadow_phys_bits - PAGE_SHIFT)); Then zap_all need not have any magic value. You can use 0/-1ull, it's readable enough. ZAP_ALL_END is also unnecessary here if you do: gfn_t max_gfn_host = 1ULL << (shadow_phys_bits - PAGE_SHIFT); bool zap_all = (start == 0 && end >= max_gfn_host); end = min(end, max_gfn_host); And as a small commit message nit, I would say "don't leak" instead of "don't skip", since that's really the effect. Paolo > kvm_lockdep_assert_mmu_lock_held(kvm, shared); > > rcu_read_lock(); > @@ -759,9 +777,10 @@ static bool zap_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root, > /* > * If this is a non-last-level SPTE that covers a larger range > * than should be zapped, continue, and zap the mappings at a > - * lower level. > + * lower level, except when zapping all SPTEs. > */ > - if ((iter.gfn < start || > + if (!zap_all && > + (iter.gfn < start || > iter.gfn + KVM_PAGES_PER_HPAGE(iter.level) > end) &&