Re: [Xen-devel] [PATCH v5] x86/p2m: use large pages for MMIO mappings

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Tuesday, January 26, 2016 12:19 AM
> 
> When mapping large BARs (e.g. the frame buffer of a graphics card) the
> overhead of establishing such mappings using only 4k pages has,
> particularly after the XSA-125 fix, become unacceptable. Alter the
> XEN_DOMCTL_memory_mapping semantics once again, so that there's no
> longer a fixed amount of guest frames that represents the upper limit
> of what a single invocation can map. Instead bound execution time by
> limiting the number of iterations (regardless of page size).
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx> for VMX part.

Curious. When you say "become unacceptable", how bad is it? mostly
impact the boot time?

Thanks
Kevin

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