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[88.146.207.194]) by smtp.googlemail.com with ESMTPSA id sb24-20020a170906edd800b009887478cc88sm1357438ejb.177.2023.06.18.14.39.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 18 Jun 2023 14:39:43 -0700 (PDT) Message-ID: <2013bbae-3bdd-df61-9e4c-b0c9dcf8b5a9@redhat.com> Date: Sun, 18 Jun 2023 23:39:42 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH v2] kvm: reuse per-vcpu stats fd to avoid vcpu interruption Content-Language: en-US To: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , Marcelo Tosatti , Markus Armbruster Cc: qemu-devel , Mark Kanda References: <87h6rab8gv.fsf@pond.sub.org> From: Paolo Bonzini In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.09, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=-1, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 6/18/23 01:00, Philippe Mathieu-Daudé wrote: >>       case STATS_TARGET_VCPU: >>           add_stats_entry(result, STATS_PROVIDER_KVM, >> -                        current_cpu->parent_obj.canonical_path, >> +                        cpu->parent_obj.canonical_path, > > Can we get a NULL deref here ... > >>                           stats_list); >>           break; >>       default: > > >>   static void query_stats_cb(StatsResultList **result, StatsTarget >> target, >> @@ -4180,7 +4180,7 @@ static void query_stats_cb(StatsResultList >> **result, StatsTarget target, >>               error_setg_errno(errp, errno, "KVM stats: ioctl failed"); >>               return; >>           } >> -        query_stats(result, target, names, stats_fd, errp); >> +        query_stats(result, target, names, stats_fd, NULL, errp); > > ... from here? No, target is STATS_TARGET_VM here. In the kernel, KVM_GET_STATS_FD could also be improved because it does not need to take vcpu->mutex. However that would not be enough; it would require QEMU changes anyway to remove run_on_cpu. So I'm queuing the patch, thanks! Paolo