Re: [PATCH] PCI: Check/Set ARI capability before setting numVFs

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Oct 04, 2017 at 08:52:58AM -0700, Tony Nguyen wrote:
> 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+ #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.  

Can you elaborate on where exactly this happens?  The only place we
explicitly set PCI_SRIOV_CTRL_ARI is in sriov_init(), which is only
called at enumeration-time.  So I'm guessing you're talking about this
path:

  ixgbe_io_slot_reset
    pci_restore_state
      pci_restore_iov_state
	sriov_restore_state
	  pci_iov_set_numvfs

where we don't set PCI_SRIOV_CTRL_ARI at all.  The fact that you say
PCI_SRIOV_CTRL_ARI isn't set until *after* pci_iov_set_numvfs() is
called suggests that it is being set *somewhere*, but I don't know
where.

> 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 | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 7492a65..a8896c7 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -497,6 +497,10 @@ 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);
>  
> -- 
> 2.9.5
>