linux-kernel - Re: [Xen-devel] [PATCH 4/6] xen/pvh: bootup and setup related changes.

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Date:	Tue, 23 Oct 2012 17:03:10 -0700
From:	Mukesh Rathor <mukesh.rathor@...cle.com>
To:	Mukesh Rathor <mukesh.rathor@...cle.com>
Cc:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Ian Campbell <Ian.Campbell@...rix.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: Re: [Xen-devel] [PATCH 4/6] xen/pvh: bootup and setup related
 changes.

On Tue, 23 Oct 2012 16:47:29 -0700
Mukesh Rathor <mukesh.rathor@...cle.com> wrote:

> On Tue, 23 Oct 2012 14:07:06 +0100
> Stefano Stabellini <stefano.stabellini@...citrix.com> wrote:
> 
> > On Mon, 22 Oct 2012, Konrad Rzeszutek Wilk wrote:
> > > On Mon, Oct 22, 2012 at 02:34:44PM +0100, Stefano Stabellini
> > > wrote:
> > > > On Sat, 20 Oct 2012, Konrad Rzeszutek Wilk wrote:
> > > > > From: Mukesh Rathor <mukesh.rathor@...cle.com>
> > > > > 
> > > > >  	for (pfn = PFN_DOWN(start); pfn < xen_max_p2m_pfn;
> > > > > pfn++) { unsigned long mfn = pfn_to_mfn(pfn);
> > > > > @@ -100,6 +104,7 @@ static unsigned long __init
> > > > > xen_do_chunk(unsigned long start, .domid        = DOMID_SELF
> > > > >  	};
> > > > >  	unsigned long len = 0;
> > > > > +	int xlated_phys =
> > > > > xen_feature(XENFEAT_auto_translated_physmap); unsigned long
> > > > > pfn; int ret;
> > > > >  
> > > > > @@ -113,7 +118,7 @@ static unsigned long __init
> > > > > xen_do_chunk(unsigned long start, continue;
> > > > >  			frame = mfn;
> > > > >  		} else {
> > > > > -			if (mfn != INVALID_P2M_ENTRY)
> > > > > +			if (!xlated_phys && mfn !=
> > > > > INVALID_P2M_ENTRY) continue;
> > > > >  			frame = pfn;
> > > > >  		}
> > > > 
> > > > Shouldn't we add a "!xlated_phys &&" to the other case as well?
> > > 
> > > No. That is handled in xen_pvh_identity_map_chunk which
> > > just does a xen_set_clr_mmio_pvh_pte call for the "released"
> > > pages. But that is a bit of ... well, extra logic. I think
> > > if we did this it would work and look much nicer:
> > 
> > Yes, I think that this version looks better
> 
> But doesn't boot:
> 
> (XEN) vmx_hybrid.c:710:d0 Dom:0 EPT violation 0x181 (r--/---), gpa
> 0x000000bf421e1c, mfn 0xffffffffffffffff, type 4. (XEN)
> p2m-ept.c:642:d0 Walking EPT tables for domain 0 gfn bf421 (XEN)
> p2m-ept.c:648:d0  gfn exceeds max_mapped_pfn 4b062 (XEN)
> vmx_hybrid.c:717:d0  --- GLA 0xffffffffff477e1c
> 
> 
> I'll have to debug it, or we can go back to the prev version, which
> I don't think is that un-pretty :).
> 

The reason being:
xen_set_identity_and_release_chunk():
NEW : > for (pfn = start_pfn; pfn <= max_pfn_mapped && pfn < end_pfn; pfn++) {

xen_pvh_identity_map_chunk():
OLD: for (pfn = start_pfn; pfn < end_pfn; pfn++)

IOW, for PVH we need to avoid testing for max_pfn_mapped, as we are
mapping the entire IO space. 

thanks
mukesh

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