linux-kernel - [PATCH 1/2] vfio/type1: Adopt fast IOTLB flush interface when unmap IOVAs

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Date:   Fri, 17 Nov 2017 15:11:19 -0600
From:   Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
To:     linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org
Cc:     joro@...tes.org, jroedel@...e.de, alex.williamson@...hat.com,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH 1/2] vfio/type1: Adopt fast IOTLB flush interface when unmap IOVAs

From: Suravee Suthikulpanit <suravee.suthikulpanit@....com>

VFIO IOMMU type1 currently upmaps IOVA pages synchronously, which requires
IOTLB flushing for every unmapping. This results in large IOTLB flushing
overhead when handling pass-through devices with a large number of mapped
IOVAs (e.g. GPUs).

This can be avoided by using the new IOTLB flushing interface.

Cc: Alex Williamson <alex.williamson@...hat.com>
Cc: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 drivers/vfio/vfio_iommu_type1.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 92155cc..28a7ab6 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -698,10 +698,12 @@ static long vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma,
 				break;
 		}
 
-		unmapped = iommu_unmap(domain->domain, iova, len);
+		unmapped = iommu_unmap_fast(domain->domain, iova, len);
 		if (WARN_ON(!unmapped))
 			break;
 
+		iommu_tlb_range_add(domain->domain, iova, len);
+
 		unlocked += vfio_unpin_pages_remote(dma, iova,
 						    phys >> PAGE_SHIFT,
 						    unmapped >> PAGE_SHIFT,
@@ -710,6 +712,7 @@ static long vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma,
 
 		cond_resched();
 	}
+	iommu_tlb_sync(domain->domain);
 
 	dma->iommu_mapped = false;
 	if (do_accounting) {
@@ -884,8 +887,11 @@ static int map_try_harder(struct vfio_domain *domain, dma_addr_t iova,
 			break;
 	}
 
-	for (; i < npage && i > 0; i--, iova -= PAGE_SIZE)
-		iommu_unmap(domain->domain, iova, PAGE_SIZE);
+	for (; i < npage && i > 0; i--, iova -= PAGE_SIZE) {
+		iommu_unmap_fast(domain->domain, iova, PAGE_SIZE);
+		iommu_tlb_range_add(domain->domain, iova, PAGE_SIZE);
+	}
+	iommu_tlb_sync(domain->domain);
 
 	return ret;
 }
-- 
1.8.3.1