Messages in this thread | | | Date | Tue, 15 Mar 2022 09:38:10 -0700 | From | Jacob Pan <> | Subject | Re: [PATCH v2 5/8] iommu: Add PASID support for DMA mapping API users |
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Hi Jason,
On Tue, 15 Mar 2022 11:35:35 -0300, Jason Gunthorpe <jgg@nvidia.com> wrote:
> On Mon, Mar 14, 2022 at 10:07:09PM -0700, Jacob Pan wrote: > > DMA mapping API is the de facto standard for in-kernel DMA. It operates > > on a per device/RID basis which is not PASID-aware. > > > > Some modern devices such as Intel Data Streaming Accelerator, PASID is > > required for certain work submissions. To allow such devices use DMA > > mapping API, we need the following functionalities: > > 1. Provide device a way to retrieve a PASID for work submission within > > the kernel > > 2. Enable the kernel PASID on the IOMMU for the device > > 3. Attach the kernel PASID to the device's default DMA domain, let it > > be IOVA or physical address in case of pass-through. > > > > This patch introduces a driver facing API that enables DMA API > > PASID usage. Once enabled, device drivers can continue to use DMA APIs > > as is. There is no difference in dma_handle between without PASID and > > with PASID. > > > > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com> > > drivers/iommu/dma-iommu.c | 65 +++++++++++++++++++++++++++++++++++++++ > > include/linux/dma-iommu.h | 7 +++++ > > include/linux/iommu.h | 9 ++++++ > > 3 files changed, 81 insertions(+) > > > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > > index b22034975301..d0ff1a34b1b6 100644 > > +++ b/drivers/iommu/dma-iommu.c > > @@ -39,6 +39,8 @@ enum iommu_dma_cookie_type { > > IOMMU_DMA_MSI_COOKIE, > > }; > > > > +static DECLARE_IOASID_SET(iommu_dma_pasid); > > + > > struct iommu_dma_cookie { > > enum iommu_dma_cookie_type type; > > union { > > @@ -370,6 +372,69 @@ void iommu_put_dma_cookie(struct iommu_domain > > *domain) domain->iova_cookie = NULL; > > } > > > > +/** > > + * iommu_enable_pasid_dma --Enable in-kernel DMA request with PASID > > + * @dev: Device to be enabled > > + * > > + * DMA request with PASID will be mapped the same way as the legacy > > DMA. > > + * If the device is in pass-through, PASID will also pass-through. If > > the > > + * device is in IOVA map, the supervisor PASID will point to the same > > IOVA > > + * page table. > > + * > > + * @return the kernel PASID to be used for DMA or INVALID_IOASID on > > failure > > + */ > > +int iommu_enable_pasid_dma(struct device *dev, ioasid_t *pasid) > > +{ > > + struct iommu_domain *dom; > > + ioasid_t id, max; > > + int ret; > > + > > + dom = iommu_get_domain_for_dev(dev); > > + if (!dom || !dom->ops || !dom->ops->attach_dev_pasid) > > + return -ENODEV; > > Given the purpose of this API I think it should assert that the device > has the DMA API in-use using the machinery from the other series. > > ie this should not be used to clone non-DMA API iommu_domains.. > Let me try to confirm the specific here. I should check domain type and rejects all others except IOMMU_DOMAIN_DMA type, right? Should also allow IOMMU_DOMAIN_IDENTITY.
That makes sense.
> > diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h > > index 24607dc3c2ac..e6cb9b52a420 100644 > > +++ b/include/linux/dma-iommu.h > > @@ -18,6 +18,13 @@ int iommu_get_dma_cookie(struct iommu_domain > > *domain); int iommu_get_msi_cookie(struct iommu_domain *domain, > > dma_addr_t base); void iommu_put_dma_cookie(struct iommu_domain > > *domain); > > +/* > > + * For devices that can do DMA request with PASID, setup a system > > PASID. > > + * Address modes (IOVA, PA) are selected by the platform code. > > + */ > > +int iommu_enable_pasid_dma(struct device *dev, ioasid_t *pasid); > > +void iommu_disable_pasid_dma(struct device *dev, ioasid_t pasid); > > The functions already have a kdoc, don't need two.. > Good point!
Thanks,
Jacob
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