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Message-ID: <8800236c103839e7996a2d976aeada97@walle.cc>
Date: Thu, 04 Aug 2022 14:56:55 +0200
From: Michael Walle <michael@...le.cc>
To: Ajay.Kathat@...rochip.com
Cc: David.Laight@...lab.com, Claudiu.Beznea@...rochip.com,
kvalo@...nel.org, davem@...emloft.net, edumazet@...gle.com,
kuba@...nel.org, pabeni@...hat.com, linux-wireless@...r.kernel.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
mwalle@...nel.org
Subject: Re: [PATCH] wilc1000: fix DMA on stack objects
Am 2022-08-04 14:43, schrieb Ajay.Kathat@...rochip.com:
> On 04/08/22 12:52, Michael Walle wrote:
>> EXTERNAL EMAIL: Do not click links or open attachments unless you know
>> the content is safe
>>
>> Am 2022-07-29 17:39, schrieb Ajay.Kathat@...rochip.com:
>>> On 29/07/22 20:28, Michael Walle wrote:
>>>> EXTERNAL EMAIL: Do not click links or open attachments unless you
>>>> know
>>>> the content is safe
>>>>
>>>> Am 29. Juli 2022 11:51:12 MESZ schrieb David Laight
>>>> <David.Laight@...LAB.COM>:
>>>>> From: Michael Walle
>>>>>> Sent: 28 July 2022 16:21
>>>>>>
>>>>>> From: Michael Walle <mwalle@...nel.org>
>>>>>>
>>>>>> Sometimes wilc_sdio_cmd53() is called with addresses pointing to
>>>>>> an
>>>>>> object on the stack. E.g. wilc_sdio_write_reg() will call it with
>>>>>> an
>>>>>> address pointing to one of its arguments. Detect whether the
>>>>>> buffer
>>>>>> address is not DMA-able in which case a bounce buffer is used. The
>>>>>> bounce
>>>>>> buffer itself is protected from parallel accesses by
>>>>>> sdio_claim_host().
>>>>>>
>>>>>> Fixes: 5625f965d764 ("wilc1000: move wilc driver out of staging")
>>>>>> Signed-off-by: Michael Walle <mwalle@...nel.org>
>>>>>> ---
>>>>>> The bug itself probably goes back way more, but I don't know if it
>>>>>> makes
>>>>>> any sense to use an older commit for the Fixes tag. If so, please
>>>>>> suggest
>>>>>> one.
>>>>>>
>>>>>> The bug leads to an actual error on an imx8mn SoC with 1GiB of
>>>>>> RAM.
>>>>>> But the
>>>>>> error will also be catched by CONFIG_DEBUG_VIRTUAL:
>>>>>> [ 9.817512] virt_to_phys used for non-linear address:
>>>>>> (____ptrval____) (0xffff80000a94bc9c)
>>>>>>
>>>>>> .../net/wireless/microchip/wilc1000/sdio.c | 28
>>>>>> ++++++++++++++++---
>>>>>> 1 file changed, 24 insertions(+), 4 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/net/wireless/microchip/wilc1000/sdio.c
>>>>>> b/drivers/net/wireless/microchip/wilc1000/sdio.c
>>>>>> index 7962c11cfe84..e988bede880c 100644
>>>>>> --- a/drivers/net/wireless/microchip/wilc1000/sdio.c
>>>>>> +++ b/drivers/net/wireless/microchip/wilc1000/sdio.c
>>>>>> @@ -27,6 +27,7 @@ struct wilc_sdio {
>>>>>> bool irq_gpio;
>>>>>> u32 block_size;
>>>>>> int has_thrpt_enh3;
>>>>>> + u8 *dma_buffer;
>>>>>> };
>>>>>>
>>>>>> struct sdio_cmd52 {
>>>>>> @@ -89,6 +90,9 @@ static int wilc_sdio_cmd52(struct wilc *wilc,
>>>>>> struct sdio_cmd52 *cmd)
>>>>>> static int wilc_sdio_cmd53(struct wilc *wilc, struct sdio_cmd53
>>>>>> *cmd)
>>>>>> {
>>>>>> struct sdio_func *func = container_of(wilc->dev, struct
>>>>>> sdio_func, dev);
>>>>>> + struct wilc_sdio *sdio_priv = wilc->bus_data;
>>>>>> + bool need_bounce_buf = false;
>>>>>> + u8 *buf = cmd->buffer;
>>>>>> int size, ret;
>>>>>>
>>>>>> sdio_claim_host(func);
>>>>>> @@ -100,12 +104,20 @@ static int wilc_sdio_cmd53(struct wilc
>>>>>> *wilc,
>>>>>> struct sdio_cmd53 *cmd)
>>>>>> else
>>>>>> size = cmd->count;
>>>>>>
>>>>>> + if ((!virt_addr_valid(buf) || object_is_on_stack(buf)) &&
>>>>> How cheap are the above tests?
>>>>> It might just be worth always doing the 'bounce'?
>>>> I'm not sure how cheap they are, but I don't think it costs more
>>>> than
>>>> copying the bulk data around. That's up to the maintainer to decide.
>>>
>>>
>>> I think, the above checks for each CMD53 might add up to the
>>> processing
>>> time of this function. These checks can be avoided, if we add new
>>> function similar to 'wilc_sdio_cmd53' which can be called when the
>>> local
>>> variables are used. Though we have to perform the memcpy operation
>>> which
>>> is anyway required to handle this scenario for small size data.
>>>
>>> Mostly, either the static global data or dynamically allocated buffer
>>> is
>>> used with cmd53 except wilc_sdio_write_reg, wilc_sdio_read_reg
>>> wilc_wlan_handle_txq functions.
>>>
>>> I have created a patch using the above approach which can fix this
>>> issue
>>> and will have no or minimal impact on existing functionality. The
>>> same
>>> is copied below:
>>>
>>>
>>> ---
>>> .../net/wireless/microchip/wilc1000/netdev.h | 1 +
>>> .../net/wireless/microchip/wilc1000/sdio.c | 46
>>> +++++++++++++++++--
>>> .../net/wireless/microchip/wilc1000/wlan.c | 2 +-
>>> 3 files changed, 45 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/net/wireless/microchip/wilc1000/netdev.h
>>> b/drivers/net/wireless/microchip/wilc1000/netdev.h
>>> index 43c085c74b7a..2137ef294953 100644
>>> --- a/drivers/net/wireless/microchip/wilc1000/netdev.h
>>> +++ b/drivers/net/wireless/microchip/wilc1000/netdev.h
>>> @@ -245,6 +245,7 @@ struct wilc {
>>> u8 *rx_buffer;
>>> u32 rx_buffer_offset;
>>> u8 *tx_buffer;
>>> + u32 vmm_table[WILC_VMM_TBL_SIZE];
>>>
>>> struct txq_handle txq[NQUEUES];
>>> int txq_entries;
>>> diff --git a/drivers/net/wireless/microchip/wilc1000/sdio.c
>>> b/drivers/net/wireless/microchip/wilc1000/sdio.c
>>> index 600cc57e9da2..19d4350ecc22 100644
>>> --- a/drivers/net/wireless/microchip/wilc1000/sdio.c
>>> +++ b/drivers/net/wireless/microchip/wilc1000/sdio.c
>>> @@ -28,6 +28,7 @@ struct wilc_sdio {
>>> u32 block_size;
>>> bool isinit;
>>> int has_thrpt_enh3;
>>> + u8 *dma_buffer;
>>> };
>>>
>>> struct sdio_cmd52 {
>>> @@ -117,6 +118,36 @@ static int wilc_sdio_cmd53(struct wilc *wilc,
>>> struct sdio_cmd53 *cmd)
>>> return ret;
>>> }
>>>
>>> +static int wilc_sdio_cmd53_extend(struct wilc *wilc, struct
>>> sdio_cmd53
>>> *cmd)
>>
>> If you handle all the stack cases anyway, the caller can just use
>> a bounce buffer and you don't need to duplicate the function.
>
>
> Thanks. Indeed, the duplicate function can be avoided. I will update
> the
> patch and send modified patch for the review.
> Btw, I was trying to reproduce the warning message by enabling
> CONFIG_DEBUG_VIRTUAL config but no luck. It seems enabling the config
> is
> not enough to test on my host or may be I am missing something.
Did you bring the interface up?
> I would
> need the help to test and confirm if the modified patch do solve the
> issue with imx8mn.
sure, just put me on cc and i can test it on my board.
-michael
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