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Subject: Re: [PATCH v6] i2c: virtio: add a virtio i2c frontend driver
To:     Jason Wang <jasowang@redhat.com>, linux-i2c@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
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        arnd@arndb.de, kblaiech@mellanox.com,
        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
References: <9a2086f37c0a62069b67c39a3f75941b78a0039c.1614749417.git.jie.deng@intel.com>
 <43b0842b-8b0f-1979-ed07-d6124e3a6b79@redhat.com>
From:   Jie Deng <jie.deng@intel.com>
Message-ID: <db9350b3-b847-8f54-546f-9a0bdec425d4@intel.com>
Date:   Wed, 10 Mar 2021 10:22:30 +0800
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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.