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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id y2sm2401527ejg.123.2021.04.26.05.32.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 26 Apr 2021 05:32:27 -0700 (PDT) To: Maxim Levitsky , kvm@vger.kernel.org Cc: "open list:DOCUMENTATION" , Thomas Gleixner , Jonathan Corbet , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "H. Peter Anvin" , Ingo Molnar , Borislav Petkov , Wanpeng Li , Vitaly Kuznetsov , Jim Mattson , Sean Christopherson , Joerg Roedel References: <20210426111333.967729-1-mlevitsk@redhat.com> <20210426111333.967729-5-mlevitsk@redhat.com> From: Paolo Bonzini Subject: Re: [PATCH v2 4/6] KVM: x86: Introduce KVM_GET_SREGS2 / KVM_SET_SREGS2 Message-ID: <898a9b18-4578-cb9d-ece7-f45ba5b7bb89@redhat.com> Date: Mon, 26 Apr 2021 14:32:26 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210426111333.967729-5-mlevitsk@redhat.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 26/04/21 13:13, Maxim Levitsky wrote: > + if (sregs2->flags & KVM_SREGS2_FLAGS_PDPTRS_VALID) { > + > + if (!is_pae_paging(vcpu)) > + return -EINVAL; > + > + for (i = 0 ; i < 4 ; i++) > + kvm_pdptr_write(vcpu, i, sregs2->pdptrs[i]); > + > + kvm_register_mark_dirty(vcpu, VCPU_EXREG_PDPTR); > + mmu_reset_needed = 1; > + } I think this should also have else { if (is_pae_paging(vcpu)) return -EINVAL; } but perhaps even better, check it at the beginning: if ((sregs->cr4 & X86_CR4_PAE) && !!(sregs->efer & EFER_LMA) == !!(sregs2->flags & KVM_SREGS2_FLAGS_PDPTRS_VALID)) return -EINVAL; which technically means the flag is redundant, but there is some value in having the flag and not allowing the user to shoot itself in the foot. Paolo