Re: [Xen-devel] [PATCH] Avoid race when guest switches between log dirty mode and dirty vram mode.

[Tim Deegan <tim@xxxxxxx>]

At 14:13 -0500 on 10 Dec (1355148836), Robert Phillips wrote:
> The previous code assumed the guest would be in one of three mutually 
> exclusive
> modes for bookkeeping dirty pages: (1) shadow, (2) hap utilizing the log dirty
> bitmap to support functionality such as live migrate, (3) hap utilizing the
> log dirty bitmap to track dirty vram pages.
> Races arose when a guest attempted to track dirty vram while performing live
> migrate.  (The dispatch table managed by paging_log_dirty_init() might change
> in the middle of a log dirty or a vram tracking function.)
> 
> This change allows hap log dirty and hap vram tracking to be concurrent.
> Vram tracking no longer uses the log dirty bitmap.  Instead it detects
> dirty vram pages by examining their p2m type.  The log dirty bitmap is only
> used by the log dirty code.  Because the two operations use different
> mechanisms, they are no longer mutually exclusive.
> 
> Signed-Off-By: Robert Phillips <robert.phillips@xxxxxxxxxx>

Applied; thanks for that. 

Tim.

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