Re: [Xen-devel] [PATCH] x86/mm: Improve ring management for memory events. Do not lose guest events

[Olaf Hering <olaf@xxxxxxxxx>]

On Fri, Jan 13, Andres Lagar-Cavilla wrote:

> > p2m_mem_paging_drop_page() should remain void because the caller has
> > already done its work, making it not restartable. Also it is only called
> > when a gfn is in paging state, which I'm sure can not happen without a
> > ring.
> 
> Well, the rationale is that returning an error code can only help, should
> new error conditions arise. Keep in mind that the pager and the ring can
> disappear at any time, so ENOSYS can still happen.

The ring should rather not disappear at all until ->paged_pages drops to
zero. Unless the goal is a restartable pager,
XEN_DOMCTL_MEM_EVENT_OP_PAGING_DISABLE should return -EBUSY when
->pages_pages is not zero. Then the checks in drop_page and populate can
be relaxed.

> I'll refresh and add your signed-off-by to cover the portions of the work
> that originate from your end, is that ok?

I havent finish the review yet, have to check how it may work with wait
queues in gfn_to_mfn*.

Olaf

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