Re: [Xen-devel] [PATCH] x86/shadow: don't use map_domain_page_global() on paths that may not fail

[Tim Deegan <tim@xxxxxxx>]

At 08:15 -0700 on 20 Feb (1550650529), Jan Beulich wrote:
> The assumption (according to one comment) and hope (according to
> another) that map_domain_page_global() can't fail are both wrong on
> large enough systems. Do away with the guest_vtable field altogether,
> and establish / tear down the desired mapping as necessary.
> 
> The alternatives, discarded as being undesirable, would have been to
> either crash the guest in sh_update_cr3() when the mapping fails, or to
> bubble up an error indicator, which upper layers would have a hard time
> to deal with (other than again by crashing the guest).
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

I follow your argument, so Acked-by: Tim Deegan <tim@xxxxxxx>

I would expect this to have a measurable cost on page fault times (on
configurations where global map isn't just a directmap).  It would be
good to know if that's the case.

Cheers,

Tim.


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