Re: [Xen-devel] [PATCH V6 4/4] x86/altp2m: fix display frozen when switching to a new view early

[George Dunlap <George.Dunlap@xxxxxxxxxx>]

> On Nov 14, 2018, at 8:40 PM, Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx> 
> wrote:
> 
> 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
>  and p2m_change_type_range() 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.

Sorry — actually, I think there’s yet another issue lurking here:  
p2m_finish_type_change(). I’ll poke around a bit more tomorrow.

 -George

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