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([2001:b07:6468:f312:b0e5:c632:a580:8b9a]) by smtp.gmail.com with ESMTPSA id c25sm32897wml.46.2020.06.29.08.05.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Jun 2020 08:05:46 -0700 (PDT) Subject: Re: [RFC v2 0/1] memory: Delete assertion in memory_region_unregister_iommu_notifier To: =?UTF-8?Q?Eugenio_P=c3=a9rez?= , qemu-devel@nongnu.org References: <20200626064122.9252-1-eperezma@redhat.com> From: Paolo Bonzini Message-ID: <52d97ca5-7dbd-3178-64d6-509a8f096f0b@redhat.com> Date: Mon, 29 Jun 2020 17:05:45 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200626064122.9252-1-eperezma@redhat.com> Content-Language: en-US X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=205.139.110.61; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/29 01:06:01 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Jason Wang , Avi Kivity , Peter Xu , Juan Quintela Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 26/06/20 08:41, Eugenio Pérez wrote: > If we examinate *entry in frame 4 of backtrace: > *entry = {target_as = 0x555556f6c050, iova = 0x0, translated_addr = 0x0, > addr_mask = 0xffffffffffffffff, perm = 0x0} > > Which (I think) tries to invalidate all the TLB registers of the device. > > Just deleting that assert is enough for the VM to start and communicate > using IOMMU, but maybe a better alternative is possible. We could move > it to the caller functions in other cases than IOMMU invalidation, or > make it conditional only if not invalidating. Yes, I think moving it up in the call stack is better. I cannot say where because the backtrace was destroyed by git (due to lines starting with "#"). Paolo > Any comment would be appreciated. Thanks! > > Guest kernel version: kernel-3.10.0-1151.el7.x86_64 > > Bug reference: https://bugs.launchpad.net/qemu/+bug/1885175 > > v2: Actually delete assertion instead of just commenting out using C99 > > Eugenio Pérez (1): > memory: Delete assertion in memory_region_unregister_iommu_notifier > > memory.c | 2 -- > 1 file changed, 2 deletions(-) >