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Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Subject: Re: [PATCH 2/4] dma-iommu: Add iommu_dma_opt_mapping_size() Content-Language: en-US To: John Garry , joro@8bytes.org, will@kernel.org, jejb@linux.ibm.com, martin.petersen@oracle.com, hch@lst.de, m.szyprowski@samsung.com, robin.murphy@arm.com Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org, iommu@lists.linux-foundation.org, linux-scsi@vger.kernel.org, liyihang6@hisilicon.com, chenxiang66@hisilicon.com, thunder.leizhen@huawei.com References: <1653035003-70312-1-git-send-email-john.garry@huawei.com> <1653035003-70312-3-git-send-email-john.garry@huawei.com> From: Damien Le Moal Organization: Western Digital Research In-Reply-To: <1653035003-70312-3-git-send-email-john.garry@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 5/20/22 17:23, John Garry wrote: > Add the IOMMU callback for DMA mapping API dma_opt_mapping_size(), which > allows the drivers to know the optimal mapping limit and thus limit the > requested IOVA lengths. > > This value is based on the IOVA rcache range limit, as IOVAs allocated > above this limit must always be newly allocated, which may be quite slow. > > Signed-off-by: John Garry > --- > drivers/iommu/dma-iommu.c | 6 ++++++ > drivers/iommu/iova.c | 5 +++++ > include/linux/iova.h | 2 ++ > 3 files changed, 13 insertions(+) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index 09f6e1c0f9c0..f619e41b9172 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -1442,6 +1442,11 @@ static unsigned long iommu_dma_get_merge_boundary(struct device *dev) > return (1UL << __ffs(domain->pgsize_bitmap)) - 1; > } > > +static size_t iommu_dma_opt_mapping_size(void) > +{ > + return iova_rcache_range(); > +} > + > static const struct dma_map_ops iommu_dma_ops = { > .alloc = iommu_dma_alloc, > .free = iommu_dma_free, > @@ -1462,6 +1467,7 @@ static const struct dma_map_ops iommu_dma_ops = { > .map_resource = iommu_dma_map_resource, > .unmap_resource = iommu_dma_unmap_resource, > .get_merge_boundary = iommu_dma_get_merge_boundary, > + .opt_mapping_size = iommu_dma_opt_mapping_size, > }; > > /* > diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c > index db77aa675145..9f00b58d546e 100644 > --- a/drivers/iommu/iova.c > +++ b/drivers/iommu/iova.c > @@ -26,6 +26,11 @@ static unsigned long iova_rcache_get(struct iova_domain *iovad, > static void free_cpu_cached_iovas(unsigned int cpu, struct iova_domain *iovad); > static void free_iova_rcaches(struct iova_domain *iovad); > > +unsigned long iova_rcache_range(void) Why not a size_t return type ? > +{ > + return PAGE_SIZE << (IOVA_RANGE_CACHE_MAX_SIZE - 1); > +} > + > static int iova_cpuhp_dead(unsigned int cpu, struct hlist_node *node) > { > struct iova_domain *iovad; > diff --git a/include/linux/iova.h b/include/linux/iova.h > index 320a70e40233..c6ba6d95d79c 100644 > --- a/include/linux/iova.h > +++ b/include/linux/iova.h > @@ -79,6 +79,8 @@ static inline unsigned long iova_pfn(struct iova_domain *iovad, dma_addr_t iova) > int iova_cache_get(void); > void iova_cache_put(void); > > +unsigned long iova_rcache_range(void); > + > void free_iova(struct iova_domain *iovad, unsigned long pfn); > void __free_iova(struct iova_domain *iovad, struct iova *iova); > struct iova *alloc_iova(struct iova_domain *iovad, unsigned long size, -- Damien Le Moal Western Digital Research