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Peter Anvin" , Joerg Roedel , Robin Murphy , Alex Williamson , Shuah Khan , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kselftest@vger.kernel.org, linux-trace-kernel@vger.kernel.org, x86@kernel.org References: <20260720111259.122911-1-dwmw2@infradead.org> <20261005095552.52748-1-griffoul@gmail.com> <20261005095552.52748-4-griffoul@gmail.com> Content-Language: en-US From: =?UTF-8?Q?Christian_K=C3=B6nig?= In-Reply-To: <20261005095552.52748-4-griffoul@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: YT4PR01CA0304.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:10e::20) To PH7PR12MB5685.namprd12.prod.outlook.com (2603:10b6:510:13c::22) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH7PR12MB5685:EE_|BY5PR12MB4228:EE_ X-MS-Office365-Filtering-Correlation-Id: e3cefb0a-155e-4bd5-fb0d-08df22c8aca4 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|1800799024|366016|376014|7416014|18002099003|22082099003|10067099003|4143699003|11063799006|56012099006; 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An exporter that changes one part of its memory cannot > say which bytes changed, so importers throw away mappings that are > still valid. > > Add an exporter helper that invalidates a byte range, and an importer > callback that receives it. The callback means that the address, the > attributes or the backing of the range changed. If part of the range is > no longer backed, get_phys() returns -ENOENT for it. Importers must stop > using their old answer before the callback returns. Importers that do > not implement the callback still receive a whole-buffer invalidation. Yeah that is exactly one of the reasons why we don't allow that. Clear NAK to the whole approach. See the reply to patch #2 for a detailed description. Regards, Christian. > > Signed-off-by: Fred Griffoul > --- > drivers/dma-buf/dma-buf.c | 30 ++++++++++++++++++++++++++++++ > include/linux/dma-buf.h | 16 ++++++++++++++++ > 2 files changed, 46 insertions(+) > > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > index 66b85d53ed22..e7010163eb2f 100644 > --- a/drivers/dma-buf/dma-buf.c > +++ b/drivers/dma-buf/dma-buf.c > @@ -1389,6 +1389,36 @@ void dma_buf_invalidate_mappings(struct dma_buf *dmabuf) > } > EXPORT_SYMBOL_NS_GPL(dma_buf_invalidate_mappings, "DMA_BUF"); > > +/** > + * dma_buf_invalidate_mappings_range - notify attachments that a range changed > + * @dmabuf: buffer whose layout changed > + * @offset: first changed byte > + * @length: number of changed bytes > + * > + * Importers with a ranged callback stop using their old mappings of the range > + * before returning. Other importers receive the existing whole-buffer > + * callback, which is correct but coarser. The reservation lock must be held. > + */ > +void dma_buf_invalidate_mappings_range(struct dma_buf *dmabuf, > + unsigned long offset, > + unsigned long length) > +{ > + struct dma_buf_attachment *attach; > + > + dma_resv_assert_held(dmabuf->resv); > + list_for_each_entry(attach, &dmabuf->attachments, node) { > + const struct dma_buf_attach_ops *ops = attach->importer_ops; > + > + if (!ops) > + continue; > + if (ops->invalidate_mappings_range) > + ops->invalidate_mappings_range(attach, offset, length); > + else if (ops->invalidate_mappings) > + ops->invalidate_mappings(attach); > + } > +} > +EXPORT_SYMBOL_NS_GPL(dma_buf_invalidate_mappings_range, "DMA_BUF"); > + > /** > * dma_buf_get_phys - describe the run that starts at an offset > * @attach: attachment to query > diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h > index b223962e20c2..55c3fe60a0ba 100644 > --- a/include/linux/dma-buf.h > +++ b/include/linux/dma-buf.h > @@ -485,6 +485,19 @@ struct dma_buf_attach_ops { > * required behavior. > */ > void (*invalidate_mappings)(struct dma_buf_attachment *attach); > + > + /** > + * @invalidate_mappings_range: [optional] a byte range changed > + * > + * The exporter changed the address, attributes or backing of > + * [@offset, @offset + @length). The importer must stop using its old > + * answer for that range before returning. > + * Importers without this callback receive @invalidate_mappings for > + * the whole buffer instead. > + */ > + void (*invalidate_mappings_range)(struct dma_buf_attachment *attach, > + unsigned long offset, > + unsigned long length); > }; > > /** > @@ -600,6 +613,9 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *, > void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *, > enum dma_data_direction); > void dma_buf_invalidate_mappings(struct dma_buf *dma_buf); > +void dma_buf_invalidate_mappings_range(struct dma_buf *dma_buf, > + unsigned long offset, > + unsigned long length); > bool dma_buf_attach_revocable(struct dma_buf_attachment *attach); > /* bits 0-7: memory type (a value, not flags) */ > #define DMA_BUF_PHYS_ATTR_TYPE_MASK GENMASK(7, 0) > -- > 2.47.3 >