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From: Kirti Wankhede <kwankhede@nvidia.com>
To: <alex.williamson@redhat.com>, <cjia@nvidia.com>
Cc: Zhengxiao.zx@Alibaba-inc.com, kevin.tian@intel.com,
	yi.l.liu@intel.com, yan.y.zhao@intel.com, kvm@vger.kernel.org,
	eskultet@redhat.com, ziye.yang@intel.com, qemu-devel@nongnu.org,
	cohuck@redhat.com, shuangtai.tst@alibaba-inc.com,
	dgilbert@redhat.com, zhi.a.wang@intel.com, mlevitsk@redhat.com,
	pasic@linux.ibm.com, aik@ozlabs.ru,
	Kirti Wankhede <kwankhede@nvidia.com>,
	eauger@redhat.com, felipe@nutanix.com,
	jonathan.davies@nutanix.com, changpeng.liu@intel.com,
	Ken.Xue@amd.com
Subject: [PATCH v15 Kernel 2/7] vfio iommu: Remove atomicity of ref_count of pinned pages
Date: Fri, 20 Mar 2020 01:46:39 +0530
Message-ID: <1584649004-8285-3-git-send-email-kwankhede@nvidia.com> (raw)
In-Reply-To: <1584649004-8285-1-git-send-email-kwankhede@nvidia.com>

vfio_pfn.ref_count is always updated by holding iommu->lock, using atomic
variable is overkill.

Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Neo Jia <cjia@nvidia.com>
---
 drivers/vfio/vfio_iommu_type1.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 9fdfae1cb17a..70aeab921d0f 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -112,7 +112,7 @@ struct vfio_pfn {
 	struct rb_node		node;
 	dma_addr_t		iova;		/* Device address */
 	unsigned long		pfn;		/* Host pfn */
-	atomic_t		ref_count;
+	unsigned int		ref_count;
 };
 
 struct vfio_regions {
@@ -233,7 +233,7 @@ static int vfio_add_to_pfn_list(struct vfio_dma *dma, dma_addr_t iova,
 
 	vpfn->iova = iova;
 	vpfn->pfn = pfn;
-	atomic_set(&vpfn->ref_count, 1);
+	vpfn->ref_count = 1;
 	vfio_link_pfn(dma, vpfn);
 	return 0;
 }
@@ -251,7 +251,7 @@ static struct vfio_pfn *vfio_iova_get_vfio_pfn(struct vfio_dma *dma,
 	struct vfio_pfn *vpfn = vfio_find_vpfn(dma, iova);
 
 	if (vpfn)
-		atomic_inc(&vpfn->ref_count);
+		vpfn->ref_count++;
 	return vpfn;
 }
 
@@ -259,7 +259,8 @@ static int vfio_iova_put_vfio_pfn(struct vfio_dma *dma, struct vfio_pfn *vpfn)
 {
 	int ret = 0;
 
-	if (atomic_dec_and_test(&vpfn->ref_count)) {
+	vpfn->ref_count--;
+	if (!vpfn->ref_count) {
 		ret = put_pfn(vpfn->pfn, dma->prot);
 		vfio_remove_from_pfn_list(dma, vpfn);
 	}
-- 
2.7.0



  parent reply index

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-19 20:16 [PATCH v15 Kernel 0/7] KABIs to support migration for VFIO devices Kirti Wankhede
2020-03-19 20:16 ` [PATCH v15 Kernel 1/7] vfio: KABI for migration interface for device state Kirti Wankhede
2020-03-23 20:30   ` Auger Eric
2020-03-24 19:31     ` Kirti Wankhede
2020-03-26  9:33   ` Christoph Hellwig
2020-03-26 21:39     ` Kirti Wankhede
2020-03-19 20:16 ` Kirti Wankhede [this message]
2020-03-23 20:30   ` [PATCH v15 Kernel 2/7] vfio iommu: Remove atomicity of ref_count of pinned pages Auger Eric
2020-03-24 19:34     ` Kirti Wankhede
2020-03-19 20:16 ` [PATCH v15 Kernel 3/7] vfio iommu: Add ioctl definition for dirty pages tracking Kirti Wankhede
2020-03-23 21:11   ` Auger Eric
2020-03-24 19:49     ` Kirti Wankhede
2020-03-19 20:16 ` [PATCH v15 Kernel 4/7] vfio iommu: Implementation of ioctl " Kirti Wankhede
2020-03-19 22:57   ` Alex Williamson
2020-03-20 17:49     ` Kirti Wankhede
2020-03-20 18:01       ` Alex Williamson
2020-03-20 18:42         ` Kirti Wankhede
2020-03-20 18:59           ` Alex Williamson
2020-03-23 17:54             ` Kirti Wankhede
2020-03-23 18:44               ` Alex Williamson
2020-03-23 18:51                 ` Dr. David Alan Gilbert
2020-03-24  3:01                   ` Yan Zhao
2020-03-24  9:45                     ` Kirti Wankhede
2020-03-24 14:36                     ` Alex Williamson
2020-03-24 20:23                       ` Dr. David Alan Gilbert
2020-03-25  5:31                         ` Tian, Kevin
2020-03-19 20:16 ` [PATCH v15 Kernel 5/7] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap Kirti Wankhede
2020-03-19 20:16 ` [PATCH v15 Kernel 6/7] vfio iommu: Adds flag to indicate dirty pages tracking capability support Kirti Wankhede
2020-03-19 20:16 ` [PATCH v15 Kernel 7/7] vfio: Selective dirty page tracking if IOMMU backed device pins pages Kirti Wankhede

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