Re: [Xen-devel] [PATCH v3 1/2] kexec: use hypercall_create_continuation to protect KEXEC ops

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

On Wed, Apr 19, 2017 at 10:19:44AM -0600, Jan Beulich wrote:
> >>> On 19.04.17 at 17:54, <daniel.kiper@xxxxxxxxxx> wrote:
> > On Wed, Apr 19, 2017 at 10:47:15AM -0500, Eric DeVolder wrote:
> >> @@ -1193,6 +1194,9 @@ static int do_kexec_op_internal(unsigned long op,
> >>      if ( ret )
> >>          return ret;
> >>
> >> +    if ( test_and_set_bit(KEXEC_FLAG_IN_HYPERCALL, &kexec_flags) )
> >> +        return hypercall_create_continuation(__HYPERVISOR_kexec_op, "lh", 
> >> op, uarg);
> >> +
> >
> > I would suggest here:
> >        ASSERT(test_bit(KEXEC_FLAG_IN_HYPERCALL, &kexec_flags));
>
> You're kidding? The flag was set just in the line above. Or do you
> really mean we need to consider test_and_set_bit() not doing what
> it is supposed to do?

Yep, it looks ridiculous. However, ASSERT() in kexec_swap_images() looks almost
the same for me. So, TBH, I still do not understand need for it at all. Could
you enlighten me?

If we really need it I would put it at the beginning of every function called
from switch() in do_kexec_op_internal(). Just in case. Though I still do not
see the point for it. At least in that form.

Daniel

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