Re: [dpdk-dev] [PATCH v2] vhost: fix add_guest_pages bug

[linhaifeng <haifeng.lin@huawei.com>]

在 2016/12/6 10:28, Yuanhan Liu 写道:
> On Thu, Dec 01, 2016 at 07:42:02PM +0800, Haifeng Lin wrote:
>> When reg_size < page_size the function read in
>> rte_mem_virt2phy would not return, becausue
>> host_user_addr is invalid.
>>
>> Signed-off-by: Haifeng Lin <haifeng.lin@huawei.com>
>> ---
>> v2:
>> fix TYPO_SPELLING warning
>> ---
>>  lib/librte_vhost/vhost_user.c | 10 +++++-----
>>  1 file changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
>> index 6b83c15..ce55e85 100644
>> --- a/lib/librte_vhost/vhost_user.c
>> +++ b/lib/librte_vhost/vhost_user.c
>> @@ -447,14 +447,14 @@ add_guest_pages(struct virtio_net *dev, struct virtio_memory_region *reg,
>>  	reg_size -= size;
>>  
>>  	while (reg_size > 0) {
>> +		size = reg_size >= page_size ? page_size : reg_size;
> 
> I'd use RTE_MIN(reg_size, page_size) here. Also, this patch miss a
> fixline (http://dpdk.org/dev):
> 
>     Fixes: e246896178e6 ("vhost: get guest/host physical address mappings")
> 
> Applied to dpdk-next-virtio, with above fixed.
> 
> Thanks for the fix!
> 
> 	--yliu
> 
>>  		host_phys_addr = rte_mem_virt2phy((void *)(uintptr_t)
>>  						  host_user_addr);
>> -		add_one_guest_page(dev, guest_phys_addr, host_phys_addr,
>> -				   page_size);
>> +		add_one_guest_page(dev, guest_phys_addr, host_phys_addr, size);
>>  
>> -		host_user_addr  += page_size;
>> -		guest_phys_addr += page_size;
>> -		reg_size -= page_size;
>> +		host_user_addr  += size;
>> +		guest_phys_addr += size;
>> +		reg_size -= size;
>>  	}
>>  }
>>  
>> -- 
>> 1.8.3.1
>>
> 
> .
> 

Hi，yliu
The bug would happen like this：

        -----------------------------
        |     region                |
        -----------------------------
        :                  : remain :
 --------------            ---------------
 |  hugepage  |   ...      |   hugepage   |
 --------------            ---------------
so the remain reg_size maybe smaller than a hugepage size, and "reg_size -= page_size" is not correct.

apply all the patch?