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[88.10.103.181]) by smtp.gmail.com with ESMTPSA id p16sm8500802wru.27.2020.06.04.05.58.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 04 Jun 2020 05:58:44 -0700 (PDT) Subject: Re: [RFC PATCH] hw/virtio/vhost: re-factor vhost-section and allow DIRTY_MEMORY_CODE To: =?UTF-8?Q?Alex_Benn=c3=a9e?= , "Michael S. Tsirkin" References: <20200604111323.7458-1-alex.bennee@linaro.org> <20200604071504-mutt-send-email-mst@kernel.org> <87ftbb59vm.fsf@linaro.org> 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: <0cce5904-fe53-d7ff-93b7-095cded2caf3@redhat.com> Date: Thu, 4 Jun 2020 14:58:42 +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: <87ftbb59vm.fsf@linaro.org> 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=philmd@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/04 01:08:38 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_H2=-0.001, SPF_PASS=-0.001, URIBL_BLOCKED=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: qemu-devel@nongnu.org, Stefan Hajnoczi , "Dr . David Alan Gilbert" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/4/20 1:49 PM, Alex Bennée wrote: > > Michael S. Tsirkin writes: > >> On Thu, Jun 04, 2020 at 12:13:23PM +0100, Alex Bennée wrote: >>> The purpose of vhost_section is to identify RAM regions that need to >>> be made available to a vhost client. However when running under TCG >>> all RAM sections have DIRTY_MEMORY_CODE set which leads to problems >>> down the line. The original comment implies VGA regions are a problem >>> but doesn't explain why vhost has a problem with it. >>> >>> Re-factor the code so: >>> >>> - steps are clearer to follow >>> - reason for rejection is recorded in the trace point >>> - we allow DIRTY_MEMORY_CODE when TCG is enabled >>> >>> Signed-off-by: Alex Bennée >>> Cc: Michael S. Tsirkin >>> Cc: Dr. David Alan Gilbert >>> Cc: Stefan Hajnoczi >>> --- >>> hw/virtio/vhost.c | 46 ++++++++++++++++++++++++++++++++-------------- >>> 1 file changed, 32 insertions(+), 14 deletions(-) [...] >>> + >>> + if (memory_region_is_ram(section->mr) && !memory_region_is_rom(section->mr)) { >>> + uint8_t dirty_mask = memory_region_get_dirty_log_mask(section->mr); >>> + uint8_t handled_dirty; >>> >>> - if (result && dev->vhost_ops->vhost_backend_mem_section_filter) { >>> - result &= >>> - dev->vhost_ops->vhost_backend_mem_section_filter(dev, section); >>> + /* >>> + * Vhost doesn't handle any block which is doing dirty-tracking other >>> + * than migration; this typically fires on VGA areas. However >>> + * for TCG we also do dirty code page tracking which shouldn't >>> + * get in the way. >>> + */ >>> + handled_dirty = (1 << DIRTY_MEMORY_MIGRATION); >>> + if (tcg_enabled()) { >>> + handled_dirty |= (1 << DIRTY_MEMORY_CODE); >>> + } >> >> So DIRTY_MEMORY_CODE is only set by TCG right? Thus I'm guessing >> we can just allow this unconditionally. > > Which actually makes the test: > > if (dirty_mask & DIRTY_MEMORY_VGA) { Eh? Shouldn't this be "if (dirty_mask & (1 << DIRTY_MEMORY_VGA))"? > .. fail .. > } > > which is more in line with the comment although wouldn't fail if we > added additional DIRTY_MEMORY flags. This leads to the question what > exactly is it about DIRTY tracking that vhost doesn't like. Is it really > only avoiding having virtqueue in video RAM? Does this ever actually > happen? > > I assume boards with unified memory models where video ram is shared > with system ram just end up partitioning the memory regions? >