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From: "Liu, Yi L" <yi.l.liu@intel.com>
To: alex.williamson@redhat.com, kwankhede@nvidia.com
Cc: kevin.tian@intel.com, baolu.lu@linux.intel.com,
	yi.l.liu@intel.com, yi.y.sun@intel.com, joro@8bytes.org,
	jean-philippe.brucker@arm.com, peterx@redhat.com,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	yamada.masahiro@socionext.com, iommu@lists.linux-foundation.org,
	Liu@vger.kernel.org
Subject: [RFC v3 2/3] vfio/pci: protect cap/ecap_perm bits alloc/free with atomic op
Date: Tue, 23 Apr 2019 20:14:39 +0800	[thread overview]
Message-ID: <1556021680-2911-3-git-send-email-yi.l.liu@intel.com> (raw)
In-Reply-To: <1556021680-2911-1-git-send-email-yi.l.liu@intel.com>

There is a case in which cap_perms and ecap_perms can be reallocated
by different modules. e.g. the vfio-mdev-pci sample driver. To secure
the initialization of cap_perms and ecap_perms, this patch adds an
atomic variable to track the user of cap/ecap_perms bits. First caller
of vfio_pci_init_perm_bits() will initialize the bits. While the last
caller of vfio_pci_uninit_perm_bits() will free the bits.

Cc: Kevin Tian <kevin.tian@intel.com>
Cc: Lu Baolu <baolu.lu@linux.intel.com>
Suggested-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Liu, Yi L <yi.l.liu@intel.com>
---
 drivers/vfio/pci/vfio_pci_config.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
index e82b511..913fca6 100644
--- a/drivers/vfio/pci/vfio_pci_config.c
+++ b/drivers/vfio/pci/vfio_pci_config.c
@@ -996,11 +996,17 @@ static int __init init_pci_ext_cap_pwr_perm(struct perm_bits *perm)
 	return 0;
 }
 
+/* Track the user number of the cap/ecap perm_bits */
+atomic_t vfio_pci_perm_bits_users = ATOMIC_INIT(0);
+
 /*
  * Initialize the shared permission tables
  */
 void vfio_pci_uninit_perm_bits(void)
 {
+	if (atomic_dec_return(&vfio_pci_perm_bits_users))
+		return;
+
 	free_perm_bits(&cap_perms[PCI_CAP_ID_BASIC]);
 
 	free_perm_bits(&cap_perms[PCI_CAP_ID_PM]);
@@ -1017,6 +1023,9 @@ int __init vfio_pci_init_perm_bits(void)
 {
 	int ret;
 
+	if (atomic_inc_return(&vfio_pci_perm_bits_users) != 1)
+		return 0;
+
 	/* Basic config space */
 	ret = init_pci_cap_basic_perm(&cap_perms[PCI_CAP_ID_BASIC]);
 
-- 
2.7.4


  parent reply	other threads:[~2019-04-24 12:31 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-23 12:14 [RFC v3 0/3] vfio_pci: wrap pci device as a mediated device Liu, Yi L
2019-04-23 12:14 ` [RFC v3 1/3] vfio_pci: split vfio_pci.c into two source files Liu, Yi L
2019-05-14 16:21   ` Alex Williamson
2019-04-23 12:14 ` Liu, Yi L [this message]
2019-04-23 12:14 ` [RFC v3 3/3] smaples: add vfio-mdev-pci driver Liu, Yi L
2019-05-23  8:44 ` [RFC v3 0/3] vfio_pci: wrap pci device as a mediated device Liu, Yi L
2019-05-23 13:03   ` Alex Williamson
2019-06-09 13:40     ` Liu, Yi L

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