Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753936AbbKLJAX (ORCPT ); Thu, 12 Nov 2015 04:00:23 -0500 Received: from mail-wm0-f42.google.com ([74.125.82.42]:36052 "EHLO mail-wm0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753690AbbKLJAV (ORCPT ); Thu, 12 Nov 2015 04:00:21 -0500 Date: Thu, 12 Nov 2015 11:00:19 +0200 From: "Kirill A. Shutemov" To: Ingo Molnar Cc: "Kirill A. Shutemov" , Borislav Petkov , hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org, jgross@suse.com, konrad.wilk@oracle.com, elliott@hpe.com, boris.ostrovsky@oracle.com, Toshi Kani , Linus Torvalds Subject: Re: [PATCH] x86/mm: fix regression with huge pages on PAE Message-ID: <20151112090018.GA22481@node.shutemov.name> References: <20151110135303.GA11246@node.shutemov.name> <20151110144648.GG19187@pd.tnic> <20151110150713.GA11956@node.shutemov.name> <20151110170447.GH19187@pd.tnic> <20151111095101.GA22512@pd.tnic> <20151112074854.GA5376@gmail.com> <20151112075758.GA20702@node.shutemov.name> <20151112080059.GA6835@gmail.com> <20151112084616.EABFE19B@black.fi.intel.com> <20151112085418.GA18963@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151112085418.GA18963@gmail.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2652 Lines: 64 On Thu, Nov 12, 2015 at 09:54:18AM +0100, Ingo Molnar wrote: > > * Kirill A. Shutemov wrote: > > > diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h > > index c5b7fb2774d0..cc071c6f7d4d 100644 > > --- a/arch/x86/include/asm/page_types.h > > +++ b/arch/x86/include/asm/page_types.h > > @@ -9,19 +9,21 @@ > > #define PAGE_SIZE (_AC(1,UL) << PAGE_SHIFT) > > #define PAGE_MASK (~(PAGE_SIZE-1)) > > > > +#define PMD_PAGE_SIZE (_AC(1, UL) << PMD_SHIFT) > > +#define PMD_PAGE_MASK (~(PMD_PAGE_SIZE-1)) > > + > > +#define PUD_PAGE_SIZE (_AC(1, UL) << PUD_SHIFT) > > +#define PUD_PAGE_MASK (~(PUD_PAGE_SIZE-1)) > > + > > #define __PHYSICAL_MASK ((phys_addr_t)((1ULL << __PHYSICAL_MASK_SHIFT) - 1)) > > #define __VIRTUAL_MASK ((1UL << __VIRTUAL_MASK_SHIFT) - 1) > > > > -/* Cast PAGE_MASK to a signed type so that it is sign-extended if > > +/* Cast *PAGE_MASK to a signed type so that it is sign-extended if > > virtual addresses are 32-bits but physical addresses are larger > > (ie, 32-bit PAE). */ > > #define PHYSICAL_PAGE_MASK (((signed long)PAGE_MASK) & __PHYSICAL_MASK) > > - > > -#define PMD_PAGE_SIZE (_AC(1, UL) << PMD_SHIFT) > > -#define PMD_PAGE_MASK (~(PMD_PAGE_SIZE-1)) > > - > > -#define PUD_PAGE_SIZE (_AC(1, UL) << PUD_SHIFT) > > -#define PUD_PAGE_MASK (~(PUD_PAGE_SIZE-1)) > > +#define PHYSICAL_PMD_PAGE_MASK (((signed long)PMD_PAGE_MASK) & __PHYSICAL_MASK) > > +#define PHYSICAL_PUD_PAGE_MASK (((signed long)PUD_PAGE_MASK) & __PHYSICAL_MASK) > > that's a really odd way of writing it, 'long' is signed by default ... See the comment above (it was there before the patch). 'signed' can be considered as documentation -- we want sign-extension here. > There seems to be 150+ such cases in the kernel source though - weird. > > More importantly, how does this improve things on 32-bit PAE kernels? If I follow > the values correctly then PMD_PAGE_MASK is 'UL' i.e. 32-bit: > > > +#define PMD_PAGE_SIZE (_AC(1, UL) << PMD_SHIFT) > > +#define PMD_PAGE_MASK (~(PMD_PAGE_SIZE-1)) > > thus PHYSICAL_PMD_PAGE_MASK is 32-bit too: > > > +#define PHYSICAL_PMD_PAGE_MASK (((signed long)PMD_PAGE_MASK) & __PHYSICAL_MASK) > > so how is the bug fixed? Again, see the comment. I've checked that it generates correct value (using kernel/bounds.c). -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/