linux-kernel - Re: [PATCHv2 08/10] x86/mm: Replace compile-time checks for 5-level with runtime-time

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Message-ID: <20170718151611.rnjdhbzaaf4c3357@node.shutemov.name>
Date:   Tue, 18 Jul 2017 18:16:11 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Juergen Gross <jgross@...e.com>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Andy Lutomirski <luto@...capital.net>,
        Michal Hocko <mhocko@...nel.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 08/10] x86/mm: Replace compile-time checks for 5-level
 with runtime-time

On Tue, Jul 18, 2017 at 04:24:06PM +0200, Juergen Gross wrote:
> On 18/07/17 16:15, Kirill A. Shutemov wrote:
> > diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
> > index cab28cf2cffb..b0530184c637 100644
> > --- a/arch/x86/xen/mmu_pv.c
> > +++ b/arch/x86/xen/mmu_pv.c
> > @@ -1209,7 +1209,7 @@ static void __init xen_cleanmfnmap(unsigned long vaddr)
> >  			continue;
> >  		xen_cleanmfnmap_p4d(p4d + i, unpin);
> >  	}
> > -	if (IS_ENABLED(CONFIG_X86_5LEVEL)) {
> > +	if (!p4d_folded) {
> >  		set_pgd(pgd, __pgd(0));
> >  		xen_cleanmfnmap_free_pgtbl(p4d, unpin);
> >  	}
> 
> Xen PV guests will never run with 5-level-paging enabled. So I guess you
> can drop the complete if (IS_ENABLED(CONFIG_X86_5LEVEL)) {} block.

Thanks.

I'll do a sparate cleanup patch for this.

-- 
 Kirill A. Shutemov