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[83.57.170.65]) by smtp.gmail.com with ESMTPSA id p18sm9278524wrx.47.2020.09.10.08.29.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 10 Sep 2020 08:29:26 -0700 (PDT) Subject: Re: [PATCH v6 3/4] util/vfio-helpers: Introduce qemu_vfio_pci_init_msix_irqs() To: Stefan Hajnoczi , Alex Williamson References: <20200909142354.334859-1-philmd@redhat.com> <20200909142354.334859-4-philmd@redhat.com> <20200910104435.GA45048@stefanha-x1.localdomain> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Autocrypt: addr=philmd@redhat.com; keydata= mQINBDXML8YBEADXCtUkDBKQvNsQA7sDpw6YLE/1tKHwm24A1au9Hfy/OFmkpzo+MD+dYc+7 bvnqWAeGweq2SDq8zbzFZ1gJBd6+e5v1a/UrTxvwBk51yEkadrpRbi+r2bDpTJwXc/uEtYAB GvsTZMtiQVA4kRID1KCdgLa3zztPLCj5H1VZhqZsiGvXa/nMIlhvacRXdbgllPPJ72cLUkXf z1Zu4AkEKpccZaJspmLWGSzGu6UTZ7UfVeR2Hcc2KI9oZB1qthmZ1+PZyGZ/Dy+z+zklC0xl XIpQPmnfy9+/1hj1LzJ+pe3HzEodtlVA+rdttSvA6nmHKIt8Ul6b/h1DFTmUT1lN1WbAGxmg CH1O26cz5nTrzdjoqC/b8PpZiT0kO5MKKgiu5S4PRIxW2+RA4H9nq7nztNZ1Y39bDpzwE5Sp bDHzd5owmLxMLZAINtCtQuRbSOcMjZlg4zohA9TQP9krGIk+qTR+H4CV22sWldSkVtsoTaA2 qNeSJhfHQY0TyQvFbqRsSNIe2gTDzzEQ8itsmdHHE/yzhcCVvlUzXhAT6pIN0OT+cdsTTfif MIcDboys92auTuJ7U+4jWF1+WUaJ8gDL69ThAsu7mGDBbm80P3vvUZ4fQM14NkxOnuGRrJxO qjWNJ2ZUxgyHAh5TCxMLKWZoL5hpnvx3dF3Ti9HW2dsUUWICSQARAQABtDJQaGlsaXBwZSBN YXRoaWV1LURhdWTDqSAoUGhpbCkgPHBoaWxtZEByZWRoYXQuY29tPokCVQQTAQgAPwIbDwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4AWIQSJweePYB7obIZ0lcuio/1u3q3A3gUCXsfWwAUJ KtymWgAKCRCio/1u3q3A3ircD/9Vjh3aFNJ3uF3hddeoFg1H038wZr/xi8/rX27M1Vj2j9VH 0B8Olp4KUQw/hyO6kUxqkoojmzRpmzvlpZ0cUiZJo2bQIWnvScyHxFCv33kHe+YEIqoJlaQc JfKYlbCoubz+02E2A6bFD9+BvCY0LBbEj5POwyKGiDMjHKCGuzSuDRbCn0Mz4kCa7nFMF5Jv piC+JemRdiBd6102ThqgIsyGEBXuf1sy0QIVyXgaqr9O2b/0VoXpQId7yY7OJuYYxs7kQoXI 6WzSMpmuXGkmfxOgbc/L6YbzB0JOriX0iRClxu4dEUg8Bs2pNnr6huY2Ft+qb41RzCJvvMyu gS32LfN0bTZ6Qm2A8ayMtUQgnwZDSO23OKgQWZVglGliY3ezHZ6lVwC24Vjkmq/2yBSLakZE 6DZUjZzCW1nvtRK05ebyK6tofRsx8xB8pL/kcBb9nCuh70aLR+5cmE41X4O+MVJbwfP5s/RW 9BFSL3qgXuXso/3XuWTQjJJGgKhB6xXjMmb1J4q/h5IuVV4juv1Fem9sfmyrh+Wi5V1IzKI7 RPJ3KVb937eBgSENk53P0gUorwzUcO+ASEo3Z1cBKkJSPigDbeEjVfXQMzNt0oDRzpQqH2vp apo2jHnidWt8BsckuWZpxcZ9+/9obQ55DyVQHGiTN39hkETy3Emdnz1JVHTU0Q== Message-ID: <4df84b90-68f6-7d69-024a-30ab2af5cc7e@redhat.com> Date: Thu, 10 Sep 2020 17:29:25 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200910104435.GA45048@stefanha-x1.localdomain> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=philmd@redhat.com X-Mimecast-Spam-Score: 0.003 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8bit Content-Language: en-US Received-SPF: pass client-ip=207.211.31.120; envelope-from=philmd@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/10 08:35:50 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -56 X-Spam_score: -5.7 X-Spam_bar: ----- X-Spam_report: (-5.7 / 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=-3.576, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no 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: Kevin Wolf , Fam Zheng , qemu-devel@nongnu.org, qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Stefan, Alex. On 9/10/20 12:44 PM, Stefan Hajnoczi wrote: > On Wed, Sep 09, 2020 at 04:23:53PM +0200, Philippe Mathieu-Daudé wrote: >> +/** >> + * Initialize device MSIX IRQs and register event notifiers. >> + * @irq_count: pointer to number of MSIX IRQs to initialize >> + * @notifier: Array of @irq_count notifiers (each corresponding to a MSIX IRQ) >> + >> + * If the number of IRQs requested exceeds the available on the device, >> + * store the number of available IRQs in @irq_count and return -EOVERFLOW. >> + */ >> +int qemu_vfio_pci_init_msix_irqs(QEMUVFIOState *s, EventNotifier *notifier, >> + unsigned *irq_count, Error **errp) >> +{ >> + int r; >> + size_t irq_set_size; >> + struct vfio_irq_set *irq_set; >> + struct vfio_irq_info irq_info = { >> + .argsz = sizeof(irq_info), >> + .index = VFIO_PCI_MSIX_IRQ_INDEX >> + }; >> + >> + if (ioctl(s->device, VFIO_DEVICE_GET_IRQ_INFO, &irq_info)) { >> + error_setg_errno(errp, errno, "Failed to get device interrupt info"); >> + return -errno; >> + } >> + if (irq_info.count < *irq_count) { >> + error_setg(errp, "Not enough device interrupts available"); >> + *irq_count = irq_info.count; >> + return -EOVERFLOW; >> + } >> + if (!(irq_info.flags & VFIO_IRQ_INFO_EVENTFD)) { >> + error_setg(errp, "Device interrupt doesn't support eventfd"); >> + return -EINVAL; >> + } >> + >> + irq_set_size = sizeof(*irq_set) + *irq_count * sizeof(int32_t); >> + irq_set = g_malloc0(irq_set_size); >> + >> + /* Get to a known IRQ state */ >> + *irq_set = (struct vfio_irq_set) { >> + .argsz = irq_set_size, >> + .flags = VFIO_IRQ_SET_DATA_EVENTFD | VFIO_IRQ_SET_ACTION_TRIGGER, >> + .index = irq_info.index, >> + .start = 0, >> + .count = *irq_count, >> + }; >> + >> + for (unsigned i = 0; i < *irq_count; i++) { >> + ((int32_t *)&irq_set->data)[i] = event_notifier_get_fd(¬ifier[i]); >> + } >> + r = ioctl(s->device, VFIO_DEVICE_SET_IRQS, irq_set); >> + g_free(irq_set); >> + if (r <= 0) { >> + error_setg_errno(errp, errno, "Failed to setup device interrupts"); >> + return -errno; >> + } else if (r < *irq_count) { >> + error_setg(errp, "Not enough device interrupts available"); >> + *irq_count = r; >> + return -EOVERFLOW; >> + } > > EOVERFLOW can occur in two cases: VFIO_DEVICE_GET_IRQ_INFO and > VFIO_DEVICE_SET_IRQS. Yes. > > If it happens in the second case the notifier[] array has been > registered successfully. No, I don't think so: vfio_pci_set_msi_trigger() register the notifier only if vfio_msi_enable() succeeded (returned 0). If vfio_msi_enable() failed it returns the number of vectors available but do not register the notifiers. Alex, do you confirm? > > The caller has no way of distinguishing the two cases. Therefore the > caller doesn't know if the eventfds will be used by the kernel after > EOVERFLOW. > > If the second case can ever happen then this function should probably > call VFIO_DEVICE_SET_IRQS again with VFIO_IRQ_SET_DATA_NONE to > unregister the eventfds before returning EOVERFLOW. > > STefan >