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Subject: Re: [PATCH v6] i2c: virtio: add a virtio i2c frontend driver
To:     Jie Deng <jie.deng@intel.com>, linux-i2c@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
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        jarkko.nikula@linux.intel.com, Sergey.Semin@baikalelectronics.ru,
        rppt@kernel.org, loic.poulain@linaro.org, tali.perry1@gmail.com,
        u.kleine-koenig@pengutronix.de, bjorn.andersson@linaro.org,
        yu1.wang@intel.com, shuo.a.liu@intel.com, viresh.kumar@linaro.org,
        stefanha@redhat.com, pbonzini@redhat.com
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 <db9350b3-b847-8f54-546f-9a0bdec425d4@intel.com>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <a3d4ce55-db25-5f96-ff44-5b76edfe9e08@redhat.com>
Date:   Wed, 10 Mar 2021 11:59:09 +0800
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On 2021/3/10 10:22 上午, Jie Deng wrote:
>
> On 2021/3/4 17:15, Jason Wang wrote:
>>
>>
>>> +        }
>>> +
>>> +        if (msgs[i].flags & I2C_M_RD)
>>> +            memcpy(msgs[i].buf, req->buf, msgs[i].len);
>>
>>
>> Sorry if I had asked this before but any rason not to use msg[i].buf 
>> directly?
>>
>>
> The msg[i].buf is passed by the I2C core. I just noticed that these 
> bufs are not
> always allocated by kmalloc. They may come from the stack, which may 
> cause
> the check "sg_init_one -> sg_set_buf -> virt_addr_valid"  to fail. 
> Therefore the
> msg[i].buf is not suitable for direct use here.
>
> Regards.


Right, stack is virtually mapped.

Thanks