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Subject[PATCH v3 08/10] vfio/pci: protect cap/ecap_perm bits alloc/free
Date
This patch add a user numer track for the shared cap/ecap_perms bits,
and the alloc/free will hold a semaphore to protect the operations.
With the changes, 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. This is a preparation to have multiple cap/ecap_perms
bits users.

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 | 33 +++++++++++++++++++++++++++++++--
1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
index f0891bd..274c993 100644
--- a/drivers/vfio/pci/vfio_pci_config.c
+++ b/drivers/vfio/pci/vfio_pci_config.c
@@ -36,6 +36,13 @@
(offset >= PCI_ROM_ADDRESS && offset < PCI_ROM_ADDRESS + 4))

/*
+ * vfio_perm_bits_sem: prorects the shared perm_bits alloc/free
+ * vfio_pci_perm_bits_users: tracks the user of the shared perm_bits
+ */
+static DEFINE_SEMAPHORE(vfio_perm_bits_sem);
+static int vfio_pci_perm_bits_users;
+
+/*
* Lengths of PCI Config Capabilities
* 0: Removed from the user visible capability list
* FF: Variable length
@@ -995,7 +1002,7 @@ static int __init init_pci_ext_cap_pwr_perm(struct perm_bits *perm)
/*
* Initialize the shared permission tables
*/
-void vfio_pci_uninit_perm_bits(void)
+static void vfio_pci_uninit_perm_bits_internal(void)
{
free_perm_bits(&cap_perms[PCI_CAP_ID_BASIC]);

@@ -1009,10 +1016,30 @@ void vfio_pci_uninit_perm_bits(void)
free_perm_bits(&ecap_perms[PCI_EXT_CAP_ID_PWR]);
}

+void vfio_pci_uninit_perm_bits(void)
+{
+ down(&vfio_perm_bits_sem);
+
+ if (--vfio_pci_perm_bits_users > 0)
+ goto out;
+
+ vfio_pci_uninit_perm_bits_internal();
+
+out:
+ up(&vfio_perm_bits_sem);
+}
+
int __init vfio_pci_init_perm_bits(void)
{
int ret;

+ down(&vfio_perm_bits_sem);
+
+ if (++vfio_pci_perm_bits_users > 1) {
+ ret = 0;
+ goto out;
+ }
+
/* Basic config space */
ret = init_pci_cap_basic_perm(&cap_perms[PCI_CAP_ID_BASIC]);

@@ -1030,8 +1057,10 @@ int __init vfio_pci_init_perm_bits(void)
ecap_perms[PCI_EXT_CAP_ID_VNDR].writefn = vfio_raw_config_write;

if (ret)
- vfio_pci_uninit_perm_bits();
+ vfio_pci_uninit_perm_bits_internal();

+out:
+ up(&vfio_perm_bits_sem);
return ret;
}

--
2.7.4
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