linux-kernel - Re: [PATCH 5/6] xen/pvh: balloon and grant changes.

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Date:	Mon, 22 Oct 2012 17:40:19 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Stefano Stabellini <Stefano.Stabellini@...citrix.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"mukesh.rathor@...cle.com" <mukesh.rathor@...cle.com>,
	Ian Campbell <Ian.Campbell@...rix.com>
Subject: Re: [PATCH 5/6] xen/pvh: balloon and grant changes.

On Mon, 22 Oct 2012, Konrad Rzeszutek Wilk wrote:
> > > +
> > >  			int ret;
> > >  			ret = HYPERVISOR_update_va_mapping(
> > >  				(unsigned long)__va(pfn << PAGE_SHIFT),
> > > @@ -418,12 +420,13 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
> > >  		scrub_page(page);
> > >  
> > >  		if (xen_pv_domain() && !PageHighMem(page)) {
> > > -			ret = HYPERVISOR_update_va_mapping(
> > > -				(unsigned long)__va(pfn << PAGE_SHIFT),
> > > -				__pte_ma(0), 0);
> > > -			BUG_ON(ret);
> > > +			if (!xen_feature(XENFEAT_auto_translated_physmap)) {
> > > +				ret = HYPERVISOR_update_va_mapping(
> > > +					(unsigned long)__va(pfn << PAGE_SHIFT),
> > > +					__pte_ma(0), 0);
> > > +				BUG_ON(ret);
> > > +			}
> > >  		}
> > 
> > this change, unlike the one before, actually makes things different for
> > traditional pv domains in case PageHighMem(page).
> 
> How? He is not altering the !PageHighMem check. Just adding a check
> before the hypercall to render it nop on PVH.

sorry, you are right, I need new glasses
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