Re: [Xen-devel] [PATCH V12 3/5] x86/altp2m: fix display frozen when switching to a new view early

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

> From: Razvan Cojocaru [mailto:rcojocaru@xxxxxxxxxxxxxxx]
> Sent: Friday, December 21, 2018 1:39 AM
> 
> When an new altp2m view is created very early on guest boot, the
> display will freeze (although the guest will run normally). This
> may also happen on resizing the display. The reason is the way
> Xen currently (mis)handles logdirty VGA: it intentionally
> misconfigures VGA pages so that they will fault.
> 
> The problem is that it only does this in the host p2m. Once we
> switch to a new altp2m, the misconfigured entries will no longer
> fault, so the display will not be updated.
> 
> This patch:
> * updates ept_handle_misconfig() to use the active altp2m instead
>   of the hostp2m;
> * modifies p2m_change_entry_type_global(),
>   p2m_memory_type_changed(), p2m_change_type_range() and
>   p2m_finish_type_change() to propagate their changes to all
>   valid altp2ms.
> 
> With the introduction of altp2m fields in p2m_memory_type_changed()
> the whole function has been put under CONFIG_HVM.
> 
> Suggested-by: George Dunlap <george.dunlap@xxxxxxxxxx>
> Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
> Tested-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
> Acked-by: George Dunlap <george.dunlap@xxxxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
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