lkml.org 
[lkml]   [2022]   [Mar]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    SubjectRe: [PATCH v2 5/8] iommu: Add PASID support for DMA mapping API users
    From
    On 2022-03-15 05:07, 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.

    Surely the main point of PASIDs is to be able to use more than one of
    them? The way I expected this to work is that iommu_enable_pasid_dma()
    returns a *new* struct device representing the dev+PASID combination,
    and the driver can then pass that to subsequent DMA API and/or IOMMU API
    calls as normal, and they know to do the right thing. Automatically
    inferring a PASID for the original physical device clearly can't scale,
    and seems like a dead-end approach that only helps this one niche use-case.

    Either way, I think this is also still fundamentally an IOMMU API
    operation that belongs in iommu.[ch] - since the iommu_dma_ops
    consolidation I'd prefer to continue working towards making dma-iommu.h
    a private header just for IOMMU API internal helpers.

    Thanks,
    Robin.

    > 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
    > --- a/drivers/iommu/dma-iommu.c
    > +++ 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;
    > + max = iommu_get_dev_pasid_max(dev);
    > + if (!max)
    > + return -EINVAL;
    > +
    > + id = ioasid_alloc(&iommu_dma_pasid, 1, max, dev);
    > + if (id == INVALID_IOASID)
    > + return -ENOMEM;
    > +
    > + ret = dom->ops->attach_dev_pasid(dom, dev, id);
    > + if (ret) {
    > + ioasid_put(id);
    > + return ret;
    > + }
    > + *pasid = id;
    > +
    > + return ret;
    > +}
    > +EXPORT_SYMBOL(iommu_enable_pasid_dma);
    > +
    > +/**
    > + * iommu_disable_pasid_dma --Disable in-kernel DMA request with PASID
    > + * @dev: Device's PASID DMA to be disabled
    > + *
    > + * It is the device driver's responsibility to ensure no more incoming DMA
    > + * requests with the kernel PASID before calling this function. IOMMU driver
    > + * ensures PASID cache, IOTLBs related to the kernel PASID are cleared and
    > + * drained.
    > + *
    > + * @return 0 on success or error code on failure
    > + */
    > +void iommu_disable_pasid_dma(struct device *dev, ioasid_t pasid)
    > +{
    > + struct iommu_domain *dom;
    > +
    > + /* TODO: check the given PASID is within the ioasid_set */
    > + dom = iommu_get_domain_for_dev(dev);
    > + if (!dom->ops->detach_dev_pasid)
    > + return;
    > + dom->ops->detach_dev_pasid(dom, dev, pasid);
    > + ioasid_put(pasid);
    > +}
    > +EXPORT_SYMBOL(iommu_disable_pasid_dma);
    > +
    > /**
    > * iommu_dma_get_resv_regions - Reserved region driver helper
    > * @dev: Device from iommu_get_resv_regions()
    > diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h
    > index 24607dc3c2ac..e6cb9b52a420 100644
    > --- a/include/linux/dma-iommu.h
    > +++ 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);
    > +
    > /* Setup call for arch DMA mapping code */
    > void iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 dma_limit);
    > int iommu_dma_init_fq(struct iommu_domain *domain);
    > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
    > index fde5b933dbe3..fb011722e4f8 100644
    > --- a/include/linux/iommu.h
    > +++ b/include/linux/iommu.h
    > @@ -395,6 +395,15 @@ static inline void iommu_set_dev_pasid_max(struct device *dev,
    >
    > param->pasid_max = max;
    > }
    > +static inline ioasid_t iommu_get_dev_pasid_max(struct device *dev)
    > +{
    > + struct dev_iommu *param = dev->iommu;
    > +
    > + if (WARN_ON(!param))
    > + return 0;
    > +
    > + return param->pasid_max;
    > +}
    >
    > int iommu_device_register(struct iommu_device *iommu,
    > const struct iommu_ops *ops,

    \
     
     \ /
      Last update: 2022-03-15 12:19    [W:3.311 / U:0.012 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site