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

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Date:   Fri, 20 May 2022 14:38:12 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Jean-Philippe Brucker <jean-philippe@...aro.org>
Cc:     baolu.lu@...ux.intel.com, 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 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;
+
  	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
   *
   * 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