Virtualization - Mar 2021 - [PATCH v6] i2c: virtio: add a virtio i2c frontend driver

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.

On 2021/3/10 10:22 ??, 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