linux-kernel - [PATCH 2/3] iommu/vt-d: Apply per-device dma

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Message-Id: <20190801060156.8564-3-baolu.lu@linux.intel.com>
Date:   Thu,  1 Aug 2019 14:01:55 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>
Cc:     ashok.raj@...el.com, jacob.jun.pan@...el.com, kevin.tian@...el.com,
        Christoph Hellwig <hch@....de>,
        Robin Murphy <robin.murphy@....com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: [PATCH 2/3] iommu/vt-d: Apply per-device dma_ops

Current Intel IOMMU driver sets the system level dma_ops. This
implementation has at least the following drawbacks: 1) each
dma API will go through the IOMMU driver even the devices are
using identity mapped domains; 2) if user requests to use an
identity mapped domain (a.k.a. bypass iommu translation), the
driver might fall back to dma domain blindly if the device is
not able to address all system memory.

This sets per-device dma_ops if a device is using a dma domain.
Otherwise, use the default system level dma_ops for direct dma.

Cc: Ashok Raj <ashok.raj@...el.com>
Cc: Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc: Kevin Tian <kevin.tian@...el.com>
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 drivers/iommu/intel-iommu.c | 48 ++++++++-----------------------------
 1 file changed, 10 insertions(+), 38 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index d2ac89a2026e..609b539b93f6 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3431,43 +3431,10 @@ static struct dmar_domain *get_private_domain_for_dev(struct device *dev)
 /* Check if the dev needs to go through non-identity map and unmap process.*/
 static bool iommu_need_mapping(struct device *dev)
 {
-	int ret;
-
 	if (iommu_dummy(dev))
 		return false;
 
-	ret = identity_mapping(dev);
-	if (ret) {
-		u64 dma_mask = *dev->dma_mask;
-
-		if (dev->coherent_dma_mask && dev->coherent_dma_mask < dma_mask)
-			dma_mask = dev->coherent_dma_mask;
-
-		if (dma_mask >= dma_get_required_mask(dev))
-			return false;
-
-		/*
-		 * 32 bit DMA is removed from si_domain and fall back to
-		 * non-identity mapping.
-		 */
-		dmar_remove_one_dev_info(dev);
-		ret = iommu_request_dma_domain_for_dev(dev);
-		if (ret) {
-			struct iommu_domain *domain;
-			struct dmar_domain *dmar_domain;
-
-			domain = iommu_get_domain_for_dev(dev);
-			if (domain) {
-				dmar_domain = to_dmar_domain(domain);
-				dmar_domain->flags |= DOMAIN_FLAG_LOSE_CHILDREN;
-			}
-			get_private_domain_for_dev(dev);
-		}
-
-		dev_info(dev, "32bit DMA uses non-identity mapping\n");
-	}
-
-	return true;
+	return !identity_mapping(dev);
 }
 
 static dma_addr_t __intel_map_single(struct device *dev, phys_addr_t paddr,
@@ -4895,8 +4862,6 @@ int __init intel_iommu_init(void)
 	}
 	up_write(&dmar_global_lock);
 
-	dma_ops = &intel_dma_ops;
-
 	init_iommu_pm_ops();
 
 	for_each_active_iommu(iommu, drhd) {
@@ -5487,8 +5452,13 @@ static int intel_iommu_add_device(struct device *dev)
 		}
 	}
 
-	if (device_needs_bounce(dev))
-		set_dma_ops(dev, &bounce_dma_ops);
+	dmar_domain = find_domain(dev);
+	if (dmar_domain && !domain_type_is_si(dmar_domain)) {
+		if (device_needs_bounce(dev))
+			set_dma_ops(dev, &bounce_dma_ops);
+		else
+			set_dma_ops(dev, &intel_dma_ops);
+	}
 
 	return 0;
 }
@@ -5507,6 +5477,8 @@ static void intel_iommu_remove_device(struct device *dev)
 	iommu_group_remove_device(dev);
 
 	iommu_device_unlink(&iommu->iommu, dev);
+
+	set_dma_ops(dev, NULL);
 }
 
 static void intel_iommu_get_resv_regions(struct device *device,
-- 
2.17.1