Re: Instability issues with NetBSD-9, xen-4.11 and the xbdb backend driver

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Fri, Nov 15, 2019 at 06:01:43AM -0000, Michael van Elst wrote:
> buhrow%nfbcal.org@localhost (Brian Buhrow) writes:
> 
> >	Hello.  Here is a simple patch that I think addresses the issue I'm
> >seeing with the dom0 causing domu's to panic with biodon2 already errors
> >when errors occur with the hypervisor granting process.
> 
> Yes, but probably not correct.
> 
> Linux undos the partial grant on failure, it also handles the
> special status GNTST_eagain (-12) where it retries individual pages
> that failed several times with exponential backoff. This status
> is returned for pages that are paged out.
> 
> No idea why we get the general error instead of a more specific one.

A debug message posted earlier suggests that the hypervisor is called with
invalid flags:
(XEN) grant_table.c:591:d0v0 Bad flags (0) or dom (0). (expected dom 0)  

flags should be at last GNTMAP_host_map (2) 
No idea how it could end up with flags (0).

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--