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Re: [Xen-devel] How to deal with hypercalls returning -EFAULT



>>> On 14.06.18 at 10:48, <jgross@xxxxxxxx> wrote:
> On 14/06/18 10:17, Julien Grall wrote:
>> On Thu, 14 Jun 2018, 07:40 Juergen Gross, <jgross@xxxxxxxx 
>> <mailto:jgross@xxxxxxxx>> wrote:
>> 
>>     On 13/06/18 18:25, Andrew Cooper wrote:
>>     > On 13/06/18 16:27, Juergen Gross wrote:
>> 
>>     Looking more into the privcmd driver I'm rather sure now I can solve
>>     this via mmap() plus an ioctl(). So the kernel would allocate the
>>     bounce buffers and map them into user space. This will require changes
>>     only in libxencall without having to modify its external interface.
>> 
>> 
>> It looks like David Vrabel sent in 2016 a patch implementing that
>> solution [1]. It seems it has not been merged. Do you have any insight
>> why it was not merged?
> 
> No. It had all needed Acks and there were no open questions.
> 
> Thanks for the reference, I think I can just reuse the patch after some
> rebasing.

But I still wonder whether retaining references obtained through
get_user_pages_fast() across system calls is a legitimate thing to do.

Jan



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