Thanks,
I've found out the reason it page-faulting is because I used malloc() to
allocate the output buffer, which turns out to allocate lazily. Therefore
the hypervisor page-fault because the memory is still waiting to be mapped
by the kernel.
I simply touched all the allocated memory, and it works fine now.
Cheers.
On 7 November 2014 19:01, Andrew Cooper <andrew.coop...@citrix.com> wrote:
> On 07/11/14 10:57, And Dinh wrote:
>
> how does it get page fault? I made sure the output buffer at the user
> space is properly allocated with the correct size.
>
> When page fault, do I have no choice but abort? It seems calling the
> hypercall again does not solve it.
>
>
> And nothing guarentees that your userspace process is in context when Xen
> is running, or that the kernel hasn't played with the pagetables behind
> your back.
>
> You must use the hypercall buffer mechanism to avoid issues like this.
> See the hypercall implementations in libxc. In Xen, you must have a
> XEN_GUEST_HANDLE() which is an opaque reference to your buffer, and use
> copy_{to,from}_guest() rather than {to/from}_user(), which is generally
> only safe for kernel addresses.
>
> ~Andrew
>
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
