linux-kernel - Re: [PATCH v7 06/10] iommu/sva: Refactoring iommu_sva_bind/unbind

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Message-ID: <Yod6/ceSMIeela/x@myrica>
Date:   Fri, 20 May 2022 12:28:44 +0100
From:   Jean-Philippe Brucker <jean-philippe@...aro.org>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     Joerg Roedel <joro@...tes.org>, Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Vinod Koul <vkoul@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 06/10] iommu/sva: Refactoring
 iommu_sva_bind/unbind_device()

On Fri, May 20, 2022 at 02:38:12PM +0800, Baolu Lu wrote:
> On 2022/5/20 00:39, Jean-Philippe Brucker wrote:
> > > +struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
> > > +{
> > > +	struct iommu_sva_domain *sva_domain;
> > > +	struct iommu_domain *domain;
> > > +	ioasid_t max_pasid = 0;
> > > +	int ret = -EINVAL;
> > > +
> > > +	/* Allocate mm->pasid if necessary. */
> > > +	if (!dev->iommu->iommu_dev->pasids)
> > > +		return ERR_PTR(-EOPNOTSUPP);
> > > +
> > > +	if (dev_is_pci(dev)) {
> > > +		max_pasid = pci_max_pasids(to_pci_dev(dev));
> > > +		if (max_pasid < 0)
> > > +			return ERR_PTR(max_pasid);
> > > +	} else {
> > > +		ret = device_property_read_u32(dev, "pasid-num-bits",
> > > +					       &max_pasid);
> > > +		if (ret)
> > > +			return ERR_PTR(ret);
> > > +		max_pasid = (1UL << max_pasid);
> > > +	}
> > The IOMMU driver needs this PASID width information earlier, when creating
> > the PASID table (in .probe_device(), .attach_dev()). Since we're moving it
> > to the IOMMU core to avoid code duplication, it should be done earlier and
> > stored in dev->iommu
> 
> Yes, really. How about below changes?
> 
> From f1382579e8a15ca49acdf758d38fd36451ea174d Mon Sep 17 00:00:00 2001
> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Date: Mon, 28 Feb 2022 15:01:35 +0800
> Subject: [PATCH 1/1] iommu: Add pasids field in struct dev_iommu
> 
> Use this field to save the number of PASIDs that a device is able to
> consume. It is a generic attribute of a device and lifting it into the
> per-device dev_iommu struct could help to avoid the boilerplate code
> in various IOMMU drivers.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> ---
>  drivers/iommu/iommu.c | 15 +++++++++++++++
>  include/linux/iommu.h |  2 ++
>  2 files changed, 17 insertions(+)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index e49c5a5b8cc1..6b731171d42f 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -20,6 +20,7 @@
>  #include <linux/idr.h>
>  #include <linux/err.h>
>  #include <linux/pci.h>
> +#include <linux/pci-ats.h>
>  #include <linux/bitops.h>
>  #include <linux/property.h>
>  #include <linux/fsl/mc.h>
> @@ -194,6 +195,8 @@ EXPORT_SYMBOL_GPL(iommu_device_unregister);
>  static struct dev_iommu *dev_iommu_get(struct device *dev)
>  {
>  	struct dev_iommu *param = dev->iommu;
> +	u32 max_pasids = 0;
> +	int ret;
> 
>  	if (param)
>  		return param;
> @@ -202,6 +205,18 @@ static struct dev_iommu *dev_iommu_get(struct device
> *dev)
>  	if (!param)
>  		return NULL;
> 
> +	if (dev_is_pci(dev)) {
> +		ret = pci_max_pasids(to_pci_dev(dev));
> +		if (ret > 0)
> +			max_pasids = ret;
> +	} else {
> +		ret = device_property_read_u32(dev, "pasid-num-bits",
> +					       &max_pasids);
> +		if (!ret)
> +			max_pasids = (1UL << max_pasids);
> +	}
> +	param->pasids = max_pasids;
> +

we could also do a min() with the IOMMU PASID size here

>  	mutex_init(&param->lock);
>  	dev->iommu = param;
>  	return param;
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 45f274b2640d..d4296136ba75 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -371,6 +371,7 @@ struct iommu_fault_param {
>   * @fwspec:	 IOMMU fwspec data
>   * @iommu_dev:	 IOMMU device this device is linked to
>   * @priv:	 IOMMU Driver private data
> + * @pasids:	 number of supported PASIDs

'max_pasids' to stay consistent?

Thanks,
Jean

>   *
>   * TODO: migrate other per device data pointers under iommu_dev_data, e.g.
>   *	struct iommu_group	*iommu_group;
> @@ -382,6 +383,7 @@ struct dev_iommu {
>  	struct iommu_fwspec		*fwspec;
>  	struct iommu_device		*iommu_dev;
>  	void				*priv;
> +	u32				pasids;
>  };
> 
>  int iommu_device_register(struct iommu_device *iommu,
> -- 
> 2.25.1
> 
> Best regards,
> baolu