Re: [Xen-devel] kernel bootup slow issue on ovm3.1.1

[Tim Deegan <tim@xxxxxxx>]

At 15:22 +0100 on 10 Aug (1344612120), Jan Beulich wrote:
> Yeah, that CR0 write disables the caches, and that's pretty
> expensive on EPT (not sure why NPT doesn't use/need the
> same hook) when the guest has any active MMIO regions:
> vmx_set_uc_mode(), when HAP is enabled, calls
> ept_change_entry_emt_with_range(), which is a walk through
> the entire guest page tables (i.e. scales with guest size, or, to
> be precise, with the highest populated GFN).

:( That's not so great.  It can definitely be done more efficiently than
with that for() loop, and I wonder whether there isn't some better way
involving flipping a global flag somewhere.

If no EPT maintainers have commented on this by Thursday I'll look into
it then.

Tim.

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