PCI: Check/Set ARI capability before setting numVFs

This fixes a bug that can occur if an AER error is encountered while SRIOV
devices are present.

This issue was seen by doing the following. Inject an AER error to a device
that has SRIOV devices.  After the device has recovered, remove the driver.
Reload the driver and enable SRIOV which causes the following crash to
occur:

kernel BUG at drivers/pci/iov.c:157!
invalid opcode: 0000 [#1] SMP
CPU: 36 PID: 2295 Comm: bash Not tainted 4.14.0-rc1+ torvalds#74
Hardware name: Supermicro X9DAi/X9DAi, BIOS 3.0a 04/29/2014
task: ffff9fa41cd45a00 task.stack: ffffb4b2036e8000
RIP: 0010:pci_iov_add_virtfn+0x2eb/0x350
RSP: 0018:ffffb4b2036ebcb8 EFLAGS: 00010286
RAX: 00000000fffffff0 RBX: ffff9fa42c1c8800 RCX: ffff9fa421ce2388
RDX: 00000000df900000 RSI: ffff9fa8214fb388 RDI: 00000000df903fff
RBP: ffffb4b2036ebd18 R08: ffff9fa421ce23b8 R09: ffffb4b2036ebc2c
R10: ffff9fa42c1a5548 R11: 000000000000058e R12: ffff9fa8214fb000
R13: ffff9fa42c1a5000 R14: ffff9fa8214fb388 R15: 0000000000000000
FS:  00007f60724b6700(0000) GS:ffff9fa82f300000(0000)
knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000559eca8b0f40 CR3: 0000000864146000 CR4: 00000000001606e0
Call Trace:
 pci_enable_sriov+0x353/0x440
 ixgbe_pci_sriov_configure+0xd5/0x1f0 [ixgbe]
 sriov_numvfs_store+0xf7/0x170
 dev_attr_store+0x18/0x30
 sysfs_kf_write+0x37/0x40
 kernfs_fop_write+0x120/0x1b0
 __vfs_write+0x37/0x170
 ? __alloc_fd+0x3f/0x170
 ? set_close_on_exec+0x30/0x70
 vfs_write+0xb5/0x1a0
 SyS_write+0x55/0xc0
 entry_SYSCALL_64_fastpath+0x1a/0xa5
RIP: 0033:0x7f6071bafc20
RSP: 002b:00007ffe7d42ba48 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000559eca8b0f30 RCX: 00007f6071bafc20
RDX: 0000000000000002 RSI: 0000559eca961f60 RDI: 0000000000000001
RBP: 00007f6071e78ae0 R08: 00007f6071e7a740 R09: 00007f60724b6700
R10: 0000000000000073 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000559eca892170
RIP: pci_iov_add_virtfn+0x2eb/0x350 RSP: ffffb4b2036ebcb8

The occurs since during AER recovery the ARI Capable Hierarchy bit,
which can affect the values for First VF Offset and VF Stride, is not set
until after pci_iov_set_numvfs() is called.  This can cause the iov
structure to be populated with values that are incorrect if the bit is
later set.   Check and set this bit, if needed, before calling
pci_iov_set_numvfs() so that the values being populated properly take
the ARI bit into account.

CC: Alexander Duyck <alexander.h.duyck@intel.com>
CC: Emil Tantilov <emil.s.tantilov@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/pci/iov.c

@@ -504,6 +504,10 @@ static void sriov_restore_state(struct pci_dev *dev)
 	if (ctrl & PCI_SRIOV_CTRL_VFE)
 		return;
 
+	if ((iov->ctrl & PCI_SRIOV_CTRL_ARI) && !(ctrl & PCI_SRIOV_CTRL_ARI))
+		pci_write_config_word(dev, iov->pos + PCI_SRIOV_CTRL,
+				      ctrl | PCI_SRIOV_CTRL_ARI);
+
 	for (i = PCI_IOV_RESOURCES; i <= PCI_IOV_RESOURCE_END; i++)
 		pci_update_resource(dev, i);