[Xen-devel] Question: dom0 electrocuted by implicitly unmapped grantrefs

[Daniel Stodden <daniel.stodden@xxxxxxxxxx>]

Hi.

Can someone explain a piece of code to me?

I'm looking at a dom0 crash dump involving the following piece in
grant_table.c:__gnttab_unmap_common

    if ( unlikely((op->rd = rd = rcu_lock_domain_by_id(dom)) == NULL) )
    {
        /* This can happen when a grant is implicitly unmapped. */
        gdprintk(XENLOG_INFO, "Could not find domain %d\n", dom);
        domain_crash(ld); /* naughty... */
        return;
    }

I assume 'implicitly unmapped' therein refers to a case where rd is gone
because ld in some or the other way already managed to tear down a
mapping without an exlicit gnttab call? This correct? Otherwise killing
ld would seem a bit rough to me :}

Either way: is domain_crash(ld) the appropriate response? Why not just
fail the op and let the caller live and learn?

Thanks.

Daniel



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