Re: [Xen-users] Issuing hypercalls from Linux Guest

[Yathindra <ydev@xxxxxxxxxxx>]

On 2/25/2013 2:23 AM, Ian Campbell wrote:
> On Sat, 2013-02-23 at 04:20 +0000, Yathindra wrote:
> > On 2/21/2013 1:37 AM, Yathindra wrote:
> > > Hi,
> > >
> > > I have defined a new hypercall in Xen hypervisor. It is similar to
> > > do_domctl()
> > > in that I pass a single argument and use XEN_GUEST_HANDLE()  to
> > > retrieve the
> > > arguments. Its currently working fine under Xen-4.3-unstable.
> > >
> > > Now I want to invoke this hypercall via Linux-3.7.5 Guest. How do I go
> > > about
> > > doing this.
> > >
> > > Thanks,
> > > Yathi
> > Hi,
> >
> > I followed a approach similar to do_physdev_op in Linux-3.7.5.
> > I have a similar set of files under include/xen/interface/ directory.
> > After plumbing everything when I execute my hypercall via Linux,
> > I get -14 (EFAULT) as the return value. I added printk's on the Xen
> > side to see if the hypercall is reaching Xen but it does not.
> >
> > Any general direction regarding this would be very helpful.
> EFAULT usually means that one of the pointers which you passed to the
> hypercall was not to correctly mapped memory.
>
> It might be useful to post your code for both sides of the equation
> (Linux & Xen).
>
> Ian.
I was passing incorrect arguments and hence the copy_from_guest() failed 
with -EFAULT.
Sorry about spamming, it was a silly mistake. Thanks for the reply Ian.

- Yathi


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