Re: [dpdk-dev] [RFC PATCH 5/5] virtio: Extend virtio-net PMD to support container environment

[Tetsuya Mukawa <mukawa@igel.co.jp>]

On 2016/01/29 18:13, Yuanhan Liu wrote:
> On Fri, Jan 29, 2016 at 04:57:23PM +0800, Yuanhan Liu wrote:
>> On Thu, Jan 21, 2016 at 08:07:58PM +0900, Tetsuya Mukawa wrote:
>>> +static int
>>> +virt_read_pci_cfg(struct virtio_hw *hw, void *buf, size_t len, off_t offset)
>>> +{
>>> +	qtest_read_pci_cfg(hw, "virtio-net", buf, len, offset);
>>> +	return 0;
>>> +}
>>> +
>>> +static void *
>>> +virt_get_mapped_addr(struct virtio_hw *hw, uint8_t bar,
>>> +		     uint32_t offset, uint32_t length)
>>> +{
>>> +	uint64_t base;
>>> +	uint64_t size;
>>> +
>>> +	if (qtest_get_bar_size(hw, "virtio-net", bar, &size) < 0) {
>>> +		PMD_INIT_LOG(ERR, "invalid bar: %u", bar);
>>> +		return NULL;
>>> +	}
>>> +
>>> +	if (offset + length < offset) {
>>> +		PMD_INIT_LOG(ERR, "offset(%u) + lenght(%u) overflows",
>>> +			offset, length);
>>> +		return NULL;
>>> +	}
>>> +
>>> +	if (offset + length > size) {
>>> +		PMD_INIT_LOG(ERR,
>>> +			"invalid cap: overflows bar space: %u > %"PRIu64,
>>> +			offset + length, size);
>>> +		return NULL;
>>> +	}
>>> +
>>> +	if (qtest_get_bar_addr(hw, "virtio-net", bar, &base) < 0) {
>>> +		PMD_INIT_LOG(ERR, "invalid bar: %u", bar);
>>> +		return NULL;
>>> +	}
>> So, I understood the usage now, and the cfg_ops abstraction doesn't look
>> good yet necessary to me.  For EAL managed pci device, bar length and
>> addr are stored at memory_resources[], and for your case, it's from the
>> qtest. And judging that it's compile time decision, I'd like it to be:
>>
>>     #ifdef /* RTE_LIBRTE_VIRTIO_HOST_MODE */
> Oops, sorry, I was wrong. Your code could be co-exist with the
> traditional virtio pmd driver, thus we can't do that.
>
> But still, I think dynamic "if ... else ..." should be better:
> there are just few places (maybe 4: bar_size, bar length, map
> device, read config) need that.

Thanks for comments.
I will use "if ... else ...." instead of introducing a cfg_ops.

Tetsuya


>
> On the other hand, if you really want to do that abstraction,
> you should go it with more fine granularity, such as the following
> methods I proposed, instead of the big one: get_cfg_addr(). In
> that way, we could avoid duplicate code.
>
> 	--yliu
>
>>     
>>     static uint32_t
>>     get_bar_size(...)
>>     {
>>     	return qtest_get_bar_size(..);
>>     }
>>     
>>     static uint64-t
>>     get_bar_addr(...)
>>     {
>>     	return qtest_get_bar_addr(..);
>>     }
>>     
>>     ...
>>     ...
>>     
>>     #else
>>     
>>     static  uint32_t
>>     get_bar_size(...)
>>     {
>>     	return dev->mem_resource[bar].addr;
>>     }
>>     
>>     ...
>>     
>>     }
>>     #endif
>>
>>
>> And then you just need do related changes at virtio_read_caps() and
>> get_cfg_addr(). That'd be much simpler, without introducing duplicate
>> code and uncessary complex.
>>
>> What do you think of that?
>>
>> 	--yliu
>>
>>> +
>>> +	return (void *)(base + offset);
>>> +}
>>> +
>>> +static const struct virtio_pci_cfg_ops virt_cfg_ops = {
>>> +	.map			= virt_map_pci_cfg,
>>> +	.unmap			= virt_unmap_pci_cfg,
>>> +	.get_mapped_addr	= virt_get_mapped_addr,
>>> +	.read			= virt_read_pci_cfg,
>>> +};
>>> +#endif /* RTE_LIBRTE_VIRTIO_HOST_MODE */