Re: [Xen-ia64-devel] Patch for PV-on-HVM for IPF

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

It might take a while for you to fix it.
Can you add comments to mark them until fix? e.g. XXX not-SMP-safe.


On Wed, Oct 11, 2006 at 02:31:39PM +0900, Doi.Tsunehisa@xxxxxxxxxxxxxx wrote:
> You (yamahata) said:
> >>> Although I haven't dug into its details, I want to check my suspicion.
> >>> The relinquishing mm code assumes that there's no racy reference.
> >>> So your patch seems too easy and not-SMP-safe to me.
> >>> For example, mm->pgd isn't protected.
> >>> What do you think?
> >> 
> >>   You are right. Hypervisor may crash in gnttab_copy code during
> >> p2m table destruction in relinquish_mm code.
> >> 
> >>   At least, mm->pgd should be nullify before destruction of the body
> >> of p2m table.
> >> 
> >>   I'll investigate it.
> > 
> > Simple setting NULL to mm->pgd before the p2m destruction isn't
> > SMP-safe again.
> 
>   I think so. I'll study more.
> 
> > Another cpu might see the p2m destruction and mm->pgd != NULL.
> > Be carefull of memory ordering.
> 
>   Thank for your comment.
> 
> - Doi
> 
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-- 
yamahata

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