Received-SPF: Pass (protection.outlook.com: domain of nvidia.com designates
 216.228.118.232 as permitted sender) receiver=protection.outlook.com;
 client-ip=216.228.118.232; helo=mail.nvidia.com; pr=C
From:   Nicolin Chen <nicolinc@nvidia.com>
To:     <jgg@nvidia.com>, <kevin.tian@intel.com>, <joro@8bytes.org>,
        <will@kernel.org>, <robin.murphy@arm.com>,
        <alex.williamson@redhat.com>, <shuah@kernel.org>
CC:     <yi.l.liu@intel.com>, <linux-kernel@vger.kernel.org>,
        <iommu@lists.linux.dev>, <kvm@vger.kernel.org>,
        <linux-kselftest@vger.kernel.org>, <baolu.lu@linux.intel.com>
Subject: [PATCH v2 05/10] iommufd: Add replace support in iommufd_access_set_ioas()
Date:   Tue, 7 Feb 2023 13:17:57 -0800
Message-ID: <931be169ff4a1f4d4f1ed060d722c2dc17ce6667.1675802050.git.nicolinc@nvidia.com>
In-Reply-To: <cover.1675802050.git.nicolinc@nvidia.com>
References: <cover.1675802050.git.nicolinc@nvidia.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Feb 2023 21:20:31.6497
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 69e8e6cd-b6b5-4d42-936e-08db095124d3
X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.232];Helo=[mail.nvidia.com]
X-MS-Exchange-CrossTenant-AuthSource: DM6NAM11FT101.eop-nam11.prod.protection.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4482
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Support an access->ioas replacement in iommufd_access_set_ioas(), which
sets the access->ioas to NULL provisionally so that any further incoming
iommufd_access_pin_pages() callback can be blocked.

Then, call access->ops->unmap() to clean up the entire iopt. To allow an
iommufd_access_unpin_pages() callback to happen via this unmap() call,
add an ioas_unpin pointer so the unpin routine won't be affected by the
"access->ioas = NULL" trick above.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
 drivers/iommu/iommufd/device.c          | 16 ++++++++++++++--
 drivers/iommu/iommufd/iommufd_private.h |  1 +
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index f4bd6f532a90..10ce47484ffa 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -509,11 +509,23 @@ int iommufd_access_set_ioas(struct iommufd_access *access, u32 ioas_id)
 		iommufd_ref_to_users(obj);
 	}
 
+	/*
+	 * Set ioas to NULL to block any further iommufd_access_pin_pages().
+	 * iommufd_access_unpin_pages() can continue using access->ioas_unpin.
+	 */
+	access->ioas = NULL;
+
 	if (cur_ioas) {
+		if (new_ioas) {
+			mutex_unlock(&access->ioas_lock);
+			access->ops->unmap(access->data, 0, ULONG_MAX);
+			mutex_lock(&access->ioas_lock);
+		}
 		iopt_remove_access(&cur_ioas->iopt, access);
 		refcount_dec(&cur_ioas->obj.users);
 	}
 
+	access->ioas_unpin = new_ioas;
 	access->ioas = new_ioas;
 	mutex_unlock(&access->ioas_lock);
 
@@ -587,11 +599,11 @@ void iommufd_access_unpin_pages(struct iommufd_access *access,
 		return;
 
 	mutex_lock(&access->ioas_lock);
-	if (!access->ioas) {
+	if (!access->ioas_unpin) {
 		mutex_unlock(&access->ioas_lock);
 		return;
 	}
-	iopt = &access->ioas->iopt;
+	iopt = &access->ioas_unpin->iopt;
 
 	down_read(&iopt->iova_rwsem);
 	iopt_for_each_contig_area(&iter, area, iopt, iova, last_iova)
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index 2f4bb106bac6..593138bb37b8 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -261,6 +261,7 @@ struct iommufd_access {
 	struct iommufd_object obj;
 	struct iommufd_ctx *ictx;
 	struct iommufd_ioas *ioas;
+	struct iommufd_ioas *ioas_unpin;
 	struct mutex ioas_lock;
 	const struct iommufd_access_ops *ops;
 	void *data;
-- 
2.39.1