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[88.21.204.71]) by smtp.gmail.com with ESMTPSA id cm26sm2483017edb.87.2020.05.27.09.27.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 May 2020 09:27:39 -0700 (PDT) Subject: Re: [PATCH] hw/vfio/common: Trace in which mode a IOMMU is opened To: Peter Xu References: <20200526173542.28710-1-philmd@redhat.com> <6c7c445d-0335-f67d-bb72-5b0c046bb247@redhat.com> <24f88212-9b32-b6dc-fcd4-685cde8bf5d7@redhat.com> <864ac8ab-e21e-393e-d1eb-08b3c4579bbf@redhat.com> <20200527161603.GF1194141@xz-x1> 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: <3e364895-e5e5-09fe-ee8c-782f3632e2b8@redhat.com> Date: Wed, 27 May 2020 18:27:38 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200527161603.GF1194141@xz-x1> 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=205.139.110.120; envelope-from=philmd@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/27 00:49:35 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=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: Auger Eric , Alex Williamson , Cornelia Huck , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 5/27/20 6:16 PM, Peter Xu wrote: > On Wed, May 27, 2020 at 05:53:16PM +0200, Philippe Mathieu-Daudé wrote: >>>>> + for (i = 0; i < ARRAY_SIZE(iommu); i++) { >>>>> + if (ioctl(container->fd, VFIO_CHECK_EXTENSION, iommu[i].type)) { >>>>> + trace_vfio_get_iommu_type(iommu[i].type, iommu[i].name); >>>> Just wondering why you want to trace the type as you now have the name >>>> string. >>> >>> You are right :) >>> >>>>> + return iommu[i].type; >>>>> } >>>>> } >>>>> + trace_vfio_get_iommu_type(-1, "Not available or not supported"); >>>> nit: from a debugging pov, this may be not needed as >>>> vfio_get_group/vfio_connect_container() fails and this leads to an error >>>> output. >> >> But you can reach this for example using No-IOMMU. If you don't mind, I >> find having this information in the trace log clearer. > > I kinda agree with Eric - AFAICT QEMU vfio-pci don't work with no-iommu, then > it seems meaningless to trace it... > > I'm not sure whether this trace is extremely helpful because syscalls like this > could be easily traced by things like strace or bpftrace as general tools (and > this information should be a one-time thing rather than dynamically changing), > no strong opinion though. Also, if we want to dump something, maybe it's > better to do in vfio_init_container() after vfio_get_iommu_type() succeeded, so > we dump which container is enabled with what type of iommu. OK. I'm a recent VFIO user so maybe I am not using the good information. This trace helps me while working on a new device feature, I didn't thought about gathering it in a production because there I'd expect things to work. Now in my case what I want is to know is if I'm using a v1 or v2 type. Maybe this information is already available in /proc or /sys and we don't need this patch...