Re: [Xen-devel] [PATCH v4] xen/grant-table: Avoid m2p_override duringmapping

[Zoltan Kiss]

On 22/01/14 18:50, Stefano Stabellini wrote:
> On Wed, 22 Jan 2014, Zoltan Kiss wrote:
> > On 22/01/14 16:39, Stefano Stabellini wrote:
> > > On Tue, 21 Jan 2014, Zoltan Kiss wrote:
> > > > @@ -121,7 +125,7 @@ static inline unsigned long mfn_to_pfn(unsigned long
> > > > mfn)
> > > >    		pfn = m2p_find_override_pfn(mfn, ~0);
> > > >    	}
> > > >
> > > > -	/*
> > > > +	/*
> > >
> > > Spurious change?
> > It removes a stray space from the original code. Not necessary, but if it's
> > there, I think we can keep it.
>
> Usually cosmetic changes are done in a separate patch, or at the very
> least they are mentioned in the commit message.
Ok, I'll mention it.
> > > > diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
> > > > index 2ae8699..0060178 100644
> > > > --- a/arch/x86/xen/p2m.c
> > > > +++ b/arch/x86/xen/p2m.c
> > > > @@ -872,15 +872,13 @@ static unsigned long mfn_hash(unsigned long mfn)
> > > >
> > > >    /* Add an MFN override for a particular page */
> > > >    int m2p_add_override(unsigned long mfn, struct page *page,
> > > > -		struct gnttab_map_grant_ref *kmap_op)
> > > > +		struct gnttab_map_grant_ref *kmap_op, unsigned long pfn)
> > >
> > > Do we really need to add another additional parameter to
> > > m2p_add_override?
> > > I would just let m2p_add_override and m2p_remove_override call
> > > page_to_pfn again. It is not that expensive.
> > Yes, because that page_to_pfn can return something different. That's why the
> > v2 patches failed.
>
> I am really curious: how can page_to_pfn return something different?
> I don't think is supposed to happen.
You call set_phys_to_machine before calling m2p* functions.

Zoli

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