Alex Nixon wrote:Hmm ok. I'll search further for a solution which fixes things more officially (and deals with the CONFIG_SMP && (NR_CPUS < CONFIG_SPLIT_PTLOCK_CPUS) case, which I just realized is also broken, and isn't fixed by this patch).
Here's the backtrace of the BUG() the patch addresses. Now you've
pointed it out - I see the asymmetry - and also suspect some ptes are
being left pinned.
I'm having trouble finding a cleaner solution which solves this but
doesn't incite more BUGs.
Perhaps you have an idea?
Right, I see. We shouldn't be pinning ptes on attachment in
xen_alloc_ptpage() if we're not using split pte locks.
J