Re: [Xen-devel] Is: [PATCH] x86/paravirt: PTE updates in k(un)map_atomic need to be synchronous, regardless of lazy_mmu mode. Was: Re: [PATCH] x86/paravirt: Partially revert "remove lazy mode in interrupts"

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Fri, Sep 30, 2011 at 11:59:46AM +0200, Stefan Bader wrote:
> On 26.09.2011 21:34, Konrad Rzeszutek Wilk wrote:
> > On Mon, Sep 26, 2011 at 09:22:21AM -0700, Jeremy Fitzhardinge wrote:
> >> On 09/26/2011 06:13 AM, Konrad Rzeszutek Wilk wrote:
> >>> which has git commit b8bcfe997e46150fedcc3f5b26b846400122fdd9.
> >>>
> >>> The unintended consequence of removing the flushing of MMU
> >>> updates when doing kmap_atomic (or kunmap_atomic) is that we can
> >>> hit a dereference bug when processing a "fork()" under a heavy loaded
> >>> machine. Specifically we can hit:
> >>
> >> The patch is all OK, but I wouldn't have headlined it as a "partial
> >> revert" - the important point is that the pte updates in k(un)map_atomic
> >> need to be synchronous, regardless of whether we're in lazy_mmu mode.
> >>
> >> The fact that b8bcfe997e4 introduced the problem is interesting to note,
> >> but only somewhat relevant to the analysis of what's being fixed here.
> > 
> > Good point. How about
> > 
> 
> Limiting the cc's for just asking about status...

Ah, got this email:

                                                                                
                                                                          
The patch titled                                                                
                                                                              
     Subject: x86/paravirt: PTE updates in k(un)map_atomic need to be 
synchronous, regardless of lazy_mmu mode                                        
        
has been added to the -mm tree.  Its filename is                                
                                                                              
     
x86-paravirt-pte-updates-in-kunmap_atomic-need-to-be-synchronous-regardless-of-lazy_mmu-mode.patch
   

so it is definitly on the train.

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