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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id q26sm3097846eja.45.2021.04.01.10.33.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 01 Apr 2021 10:33:13 -0700 (PDT) Subject: Re: [PATCH 4/6] KVM: x86: Introduce KVM_GET_SREGS2 / KVM_SET_SREGS2 To: Maxim Levitsky , kvm@vger.kernel.org Cc: "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , Jim Mattson , Vitaly Kuznetsov , Wanpeng Li , Sean Christopherson , Joerg Roedel , "H. Peter Anvin" , "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , Thomas Gleixner , Jonathan Corbet , Borislav Petkov , Ingo Molnar , "open list:DOCUMENTATION" References: <20210401141814.1029036-1-mlevitsk@redhat.com> <20210401141814.1029036-5-mlevitsk@redhat.com> <0b3a93e3d1ba6a89da327b93be2ecf47f22010d4.camel@redhat.com> From: Paolo Bonzini Message-ID: <514c1f1f-5c7d-7b27-b893-87d9b85db523@redhat.com> Date: Thu, 1 Apr 2021 19:33:12 +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: <0b3a93e3d1ba6a89da327b93be2ecf47f22010d4.camel@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/04/21 19:10, Maxim Levitsky wrote: > I haven't yet studied in depth the locking that is used in the kvm, > so I put this to be on the safe side. > > I looked at it a bit and it looks like the pdptr reading code takes > this lock because it accesses the memslots, which is not done here, > and therefore the lock is indeed not needed here. > > I need to study in depth how locking is done in kvm to be 100% sure > about this. Yes, SRCU protects reading the memslots (and therefore accessing guest memory). >> 195, not 196. > > I am also planning to add KVM_CAP_SET_GUEST_DEBUG2 for which I > used 195. Sounds good then. Paolo