[Intel-wired-lan] [PATCH] i40e: fix panic on SPARC while changing num of desc

[Bowers, AndrewX]

> -----Original Message-----
> From: Intel-wired-lan [mailto:intel-wired-lan-bounces at lists.osuosl.org] On
> Behalf Of Tushar Dave
> Sent: Wednesday, October 26, 2016 10:49 AM
> To: Kirsher, Jeffrey T <jeffrey.t.kirsher at intel.com>; intel-wired-
> lan at lists.osuosl.org; netdev at vger.kernel.org; Brandeburg, Jesse
> <jesse.brandeburg at intel.com>
> Subject: [Intel-wired-lan] [PATCH] i40e: fix panic on SPARC while changing
> num of desc
> 
> On SPARC, writel() should not be used to write directly to memory address
> but only to memory mapped I/O address otherwise it causes data access
> exception.
> 
> Commit 147e81ec75689 ("i40e: Test memory before ethtool alloc
> succeeds") introduced a code that uses memory address to fake the HW tail
> address and attempt to write to that address using writel() causes kernel
> panic on SPARC. The issue is reproduced while changing number of
> descriptors using ethtool.
> 
> This change resolves the panic by using HW read-only memory mapped I/O
> register to fake HW tail address instead memory address.
> 
> e.g.
> > ethtool -G eth2 tx 2048 rx 2048
> i40e 0000:03:00.2 eth2: Changing Tx descriptor count from 512 to 2048.
> i40e 0000:03:00.2 eth2: Changing Rx descriptor count from 512 to 2048
> sun4v_data_access_exception: ADDR[fff8001f9734a000] CTX[0000]
> TYPE[0004], going.
>               \|/ ____ \|/
>               "@'/ .. \`@"
>               /_| \__/ |_\
>                  \__U_/
> ethtool(3273): Dax [#1]
> CPU: 9 PID: 3273 Comm: ethtool Tainted: G            E
> 4.8.0-linux-net_temp+ #7
> task: fff8001f96d7a660 task.stack: fff8001f97348000
> TSTATE: 0000009911001601 TPC: 00000000103189e4 TNPC: 00000000103189e8
> Y:
> 00000000    Tainted: G            E
> TPC: <i40e_alloc_rx_buffers+0x124/0x260 [i40e]>
> g0: fff8001f4eb64000 g1: 00000000000007ff g2: fff8001f9734b92c g3:
> 00203e0000000000
> g4: fff8001f96d7a660 g5: fff8001fa6704000 g6: fff8001f97348000 g7:
> 0000000000000001
> o0: 0006000046706928 o1: 00000000db3e2000 o2: fff8001f00000000 o3:
> 0000000000002000
> o4: 0000000000002000 o5: 0000000000000001 sp: fff8001f9734afc1 ret_pc:
> 0000000010318a64
> RPC: <i40e_alloc_rx_buffers+0x1a4/0x260 [i40e]>
> l0: fff8001f4e8bffe0 l1: fff8001f4e8cffe0 l2: 00000000000007ff l3:
> 00000000ff000000
> l4: 0000000000ff0000 l5: 000000000000ff00 l6: 0000000000cda6a8 l7:
> 0000000000e822f0
> i0: fff8001f96380000 i1: 0000000000000000 i2: 00203edb00000000 i3:
> 0006000046706928
> i4: 0000000002086320 i5: 0000000000e82370 i6: fff8001f9734b071 i7:
> 00000000103062d4
> I7: <i40e_set_ringparam+0x3b4/0x540 [i40e]> Call Trace:
>  [00000000103062d4] i40e_set_ringparam+0x3b4/0x540 [i40e]
> [000000000094e2f8] dev_ethtool+0x898/0xbe0  [0000000000965570]
> dev_ioctl+0x250/0x300  [0000000000923800] sock_do_ioctl+0x40/0x60
> [000000000092427c] sock_ioctl+0x7c/0x280  [00000000005ef040]
> vfs_ioctl+0x20/0x60  [00000000005ef5d4] do_vfs_ioctl+0x194/0x4c0
> [00000000005ef974] SyS_ioctl+0x74/0xa0  [0000000000406214]
> linux_sparc_syscall+0x34/0x44 Disabling lock debugging due to kernel taint
> Caller[00000000103062d4]: i40e_set_ringparam+0x3b4/0x540 [i40e]
> Caller[000000000094e2f8]: dev_ethtool+0x898/0xbe0
> Caller[0000000000965570]: dev_ioctl+0x250/0x300
> Caller[0000000000923800]: sock_do_ioctl+0x40/0x60
> Caller[000000000092427c]: sock_ioctl+0x7c/0x280
> Caller[00000000005ef040]: vfs_ioctl+0x20/0x60
> Caller[00000000005ef5d4]: do_vfs_ioctl+0x194/0x4c0
> Caller[00000000005ef974]: SyS_ioctl+0x74/0xa0
> Caller[0000000000406214]: linux_sparc_syscall+0x34/0x44
> Caller[0000000000107154]: 0x107154
> Instruction DUMP: e43620c8
>  e436204a  c45e2038
> <c2a083a0> 82102000
>  81cfe008  90086001
>  82102000  81cfe008
> 
> Kernel panic - not syncing: Fatal exception
> 
> Signed-off-by: Tushar Dave <tushar.n.dave at oracle.com>
> ---
>  drivers/net/ethernet/intel/i40e/i40e_ethtool.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)

Tested-by: Andrew Bowers <andrewx.bowers at intel.com>