netdev - Re: [PATCH v2] net: moxa: get rid of asymmetry in DMA mapping/unmapping

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Date:   Sat, 20 Aug 2022 20:50:49 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Sergei Antonov <saproj@...il.com>
Cc:     netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
        Vladimir Oltean <olteanv@...il.com>
Subject: Re: [PATCH v2] net: moxa: get rid of asymmetry in DMA
 mapping/unmapping

On Fri, Aug 19, 2022 at 02:05:19PM +0300, Sergei Antonov wrote:
> Since priv->rx_mapping[i] is maped in moxart_mac_open(), we
> should unmap it from moxart_mac_stop(). Fixes 2 warnings.
> 
> 1. During error unwinding in moxart_mac_probe(): "goto init_fail;",
> then moxart_mac_free_memory() calls dma_unmap_single() with
> priv->rx_mapping[i] pointers zeroed.
> 
> WARNING: CPU: 0 PID: 1 at kernel/dma/debug.c:963 check_unmap+0x704/0x980
> DMA-API: moxart-ethernet 92000000.mac: device driver tries to free DMA memory it has not allocated [device address=0x0000000000000000] [size=1600 bytes]
> CPU: 0 PID: 1 Comm: swapper Not tainted 5.19.0+ #60
> Hardware name: Generic DT based system
>  unwind_backtrace from show_stack+0x10/0x14
>  show_stack from dump_stack_lvl+0x34/0x44
>  dump_stack_lvl from __warn+0xbc/0x1f0
>  __warn from warn_slowpath_fmt+0x94/0xc8
>  warn_slowpath_fmt from check_unmap+0x704/0x980
>  check_unmap from debug_dma_unmap_page+0x8c/0x9c
>  debug_dma_unmap_page from moxart_mac_free_memory+0x3c/0xa8
>  moxart_mac_free_memory from moxart_mac_probe+0x190/0x218
>  moxart_mac_probe from platform_probe+0x48/0x88
>  platform_probe from really_probe+0xc0/0x2e4
> 
> 2. After commands:
>  ip link set dev eth0 down
>  ip link set dev eth0 up
> 
> WARNING: CPU: 0 PID: 55 at kernel/dma/debug.c:570 add_dma_entry+0x204/0x2ec
> DMA-API: moxart-ethernet 92000000.mac: cacheline tracking EEXIST, overlapping mappings aren't supported
> CPU: 0 PID: 55 Comm: ip Not tainted 5.19.0+ #57
> Hardware name: Generic DT based system
>  unwind_backtrace from show_stack+0x10/0x14
>  show_stack from dump_stack_lvl+0x34/0x44
>  dump_stack_lvl from __warn+0xbc/0x1f0
>  __warn from warn_slowpath_fmt+0x94/0xc8
>  warn_slowpath_fmt from add_dma_entry+0x204/0x2ec
>  add_dma_entry from dma_map_page_attrs+0x110/0x328
>  dma_map_page_attrs from moxart_mac_open+0x134/0x320
>  moxart_mac_open from __dev_open+0x11c/0x1ec
>  __dev_open from __dev_change_flags+0x194/0x22c
>  __dev_change_flags from dev_change_flags+0x14/0x44
>  dev_change_flags from devinet_ioctl+0x6d4/0x93c
>  devinet_ioctl from inet_ioctl+0x1ac/0x25c
> 
> v1 -> v2:
> Extraneous change removed.
> 
> Fixes: 6c821bd9edc9 ("net: Add MOXA ART SoCs ethernet driver")
> Signed-off-by: Sergei Antonov <saproj@...il.com>

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew