Re: [Xen-devel] [PATCH v3] kexec: implement STATUS hypercall to check if image is loaded

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 18.01.17 at 11:37, <wei.liu2@xxxxxxxxxx> wrote:
> On Wed, Jan 18, 2017 at 03:19:49AM -0700, Jan Beulich wrote:
>> >>> On 17.01.17 at 18:29, <eric.devolder@xxxxxxxxxx> wrote:
>> > --- a/xen/common/kexec.c
>> > +++ b/xen/common/kexec.c
>> > @@ -1169,6 +1169,22 @@ static int 
>> > kexec_unload(XEN_GUEST_HANDLE_PARAM(void) uarg)
>> >      return kexec_do_unload(&unload);
>> >  }
>> >  
>> > +static int kexec_status(XEN_GUEST_HANDLE_PARAM(void) uarg)
>> > +{
>> > +    xen_kexec_status_t status;
>> > +    int base, bit;
>> > +
>> > +    if ( unlikely(copy_from_guest(&status, uarg, 1)) )
>> > +        return -EFAULT;
>> > +
>> > +    /* No need to check KEXEC_FLAG_IN_PROGRESS. */
>> > +
>> > +    if ( kexec_load_get_bits(status.type, &base, &bit) )
>> > +        return -EINVAL;
>> > +
>> > +    return test_bit(bit, &kexec_flags);
>> 
>> In the public header you promise to return zero or one here (unless
>> an error occurs), which requires the use of !!. Please see x86's
>> implementation of the function for how/when there can actually be
>> other non-zero values returned here (in particular all ones, which
>> would resolve to -EPERM).
>> 
>> > --- a/xen/include/public/kexec.h
>> > +++ b/xen/include/public/kexec.h
>> > @@ -227,6 +227,19 @@ typedef struct xen_kexec_unload {
>> >  } xen_kexec_unload_t;
>> >  DEFINE_XEN_GUEST_HANDLE(xen_kexec_unload_t);
>> >  
>> > +/*
>> > + * Figure out whether we have an image loaded. A return value of
>> > + * zero indicates no image loaded. A return value of one
>> > + * indicates an image is loaded. A negative return value
>> > + * indicates an error.
>> > + *
>> > + * Type must be one of KEXEC_TYPE_DEFAULT or KEXEC_TYPE_CRASH.
>> > + */
>> > +#define KEXEC_CMD_kexec_status 6
>> > +typedef struct xen_kexec_status {
>> > +    uint8_t type;
>> > +} xen_kexec_status_t;
>> > +DEFINE_XEN_GUEST_HANDLE(xen_kexec_status_t);
>> >  #else /* __XEN_INTERFACE_VERSION__ < 0x00040400 */
>> 
>> There was a blank line above here before your addition, and you
>> shouldn't eliminate it (making quickly scanning over the file harder).
>> 
>> I guess both items are simple enough to fix while committing.
> 
> Oops, I already committed this patch with Andrew's review. A follow-up
> patch is appreciated. Thanks.

Well, I suppose that was directed at Eric ...

Jan


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