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[34.127.75.226]) by smtp.gmail.com with ESMTPSA id s21-20020a056a00195500b004f65b15b3a0sm3234216pfk.8.2022.03.03.10.37.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Mar 2022 10:37:29 -0800 (PST) Date: Thu, 3 Mar 2022 18:37:25 +0000 From: Mingwei Zhang To: Sean Christopherson Cc: Paolo Bonzini , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , David Hildenbrand , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, David Matlack , Ben Gardon Subject: Re: [PATCH v3 11/28] KVM: x86/mmu: WARN if old _or_ new SPTE is REMOVED in non-atomic path Message-ID: References: <20220226001546.360188-1-seanjc@google.com> <20220226001546.360188-12-seanjc@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220226001546.360188-12-seanjc@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Feb 26, 2022, Sean Christopherson wrote: > WARN if the new_spte being set by __tdp_mmu_set_spte() is a REMOVED_SPTE, > which is called out by the comment as being disallowed but not actually > checked. Keep the WARN on the old_spte as well, because overwriting a > REMOVED_SPTE in the non-atomic path is also disallowed (as evidence by > lack of splats with the existing WARN). > > Fixes: 08f07c800e9d ("KVM: x86/mmu: Flush TLBs after zap in TDP MMU PF handler") > Cc: Ben Gardon > Signed-off-by: Sean Christopherson > Reviewed-by: Ben Gardon Reviewed-by: Mingwei Zhang > --- > arch/x86/kvm/mmu/tdp_mmu.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c > index 8fbf3364f116..1dcdf1a4fcc1 100644 > --- a/arch/x86/kvm/mmu/tdp_mmu.c > +++ b/arch/x86/kvm/mmu/tdp_mmu.c > @@ -640,13 +640,13 @@ static inline void __tdp_mmu_set_spte(struct kvm *kvm, struct tdp_iter *iter, > lockdep_assert_held_write(&kvm->mmu_lock); > > /* > - * No thread should be using this function to set SPTEs to the > + * No thread should be using this function to set SPTEs to or from the > * temporary removed SPTE value. > * If operating under the MMU lock in read mode, tdp_mmu_set_spte_atomic > * should be used. If operating under the MMU lock in write mode, the > * use of the removed SPTE should not be necessary. > */ > - WARN_ON(is_removed_spte(iter->old_spte)); > + WARN_ON(is_removed_spte(iter->old_spte) || is_removed_spte(new_spte)); > > kvm_tdp_mmu_write_spte(iter->sptep, new_spte); > > -- > 2.35.1.574.g5d30c73bfb-goog >