Re: [Xen-devel] [PATCH v2 1/2] libxl: Implement the handler to handle unrecoverable AER errors.

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Jul 28, 2017 at 10:15:40AM -0700, Venu Busireddy wrote:
> On 2017-07-28 16:58:13 +0100, Wei Liu wrote:
> > On Wed, Jul 26, 2017 at 07:16:38PM -0500, Venu Busireddy wrote:
> > > Implement the callback function to handle unrecoverable AER errors, and
> > > also the public APIs that can be used to register/unregister the handler.
> > > When an AER error occurs, the handler will forcibly remove the erring
> > > PCIe device from the guest.
> > > 
> > > Signed-off-by: Venu Busireddy <venu.busireddy@xxxxxxxxxx>
> > > ---
> > >  tools/libxl/libxl_event.h |  2 ++
> > >  tools/libxl/libxl_pci.c   | 85 
> > > +++++++++++++++++++++++++++++++++++++++++++++++
> > >  2 files changed, 87 insertions(+)
> > > 
> > 
> > Please also add a LIBXL_HAVE macro to libxl.h. There are plenty of
> > examples there.
> 
> I assume you meant, for example, something like:
> 
> /* LIBXL_HAVE_UNREG_AER_EVENTS_HANDLER
>  *
>  * If it is defined, libxl has a library function called
>  * libxl_unreg_aer_events_handler.
>  */
> #define LIBXL_HAVE_UNREG_AER_EVENTS_HANDLER 1
> 
> If so, I will add them in the next revision.
> 
> > > +
> > > +int libxl_reg_aer_events_handler(libxl_ctx *ctx, uint32_t domid)
> > > +{
> > > +    int rc = 0;
> > > +    char *be_path;
> > > +    GC_INIT(ctx);
> > > +
> > > +    aer_watch.domid = domid;
> > > +    be_path = 
> > > GCSPRINTF("/local/domain/0/backend/pci/%u/0/aerFailedSBDF", domid);
> > 
> > I think the best thing to do is you get the domid using
> > libxl__get_domid. Try not to hard-code 0.
> > 
> > Same for your callback function. And there are quite a few 0's that I'm
> > not sure what they stand for.
> 
> All those 0's are saying dom0's domid. Isn't dom0's domid always 0?
> If that is not the case, I can use libxl__get_domid(). Please let me
> know.

Don't assume the code will always run in dom0, so use get_domid is best.

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