Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753770AbbKXPCE (ORCPT ); Tue, 24 Nov 2015 10:02:04 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:31439 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753071AbbKXPCC (ORCPT ); Tue, 24 Nov 2015 10:02:02 -0500 Subject: Re: [PATCH] x86/mm: fix regression with huge pages on PAE To: "Kirill A. Shutemov" , Ingo Molnar 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> <20151112090018.GA22481@node.shutemov.name> 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, Toshi Kani , Linus Torvalds From: Boris Ostrovsky Message-ID: <56547B4F.6030902@oracle.com> Date: Tue, 24 Nov 2015 09:59:27 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <20151112090018.GA22481@node.shutemov.name> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2741 Lines: 64 On 11/12/2015 04:00 AM, Kirill A. Shutemov wrote: > 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 Kirill, where are we with this patch? -boris >>> @@ -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). > -- 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/