From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id D89F66B0038 for ; Thu, 28 Sep 2017 05:19:57 -0400 (EDT) Received: by mail-wr0-f197.google.com with SMTP id d6so1479327wrd.7 for ; Thu, 28 Sep 2017 02:19:57 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id k26sor709323edk.44.2017.09.28.02.19.56 for (Google Transport Security); Thu, 28 Sep 2017 02:19:56 -0700 (PDT) Date: Thu, 28 Sep 2017 12:19:54 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCHv7 02/19] mm/zsmalloc: Prepare to variable MAX_PHYSMEM_BITS Message-ID: <20170928091954.t74i542dlnejbzty@node.shutemov.name> References: <20170918105553.27914-1-kirill.shutemov@linux.intel.com> <20170918105553.27914-3-kirill.shutemov@linux.intel.com> <20170928081034.g3k3sz7pue7jnzvi@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170928081034.g3k3sz7pue7jnzvi@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Ingo Molnar , Minchan Kim , Nitin Gupta , Sergey Senozhatsky Cc: "Kirill A. Shutemov" , Ingo Molnar , Linus Torvalds , x86@kernel.org, Thomas Gleixner , "H. Peter Anvin" , Andrew Morton , Andy Lutomirski , Cyrill Gorcunov , Borislav Petkov , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Thu, Sep 28, 2017 at 10:10:34AM +0200, Ingo Molnar wrote: > > * Kirill A. Shutemov wrote: > > > With boot-time switching between paging mode we will have variable > > MAX_PHYSMEM_BITS. > > > > Let's use the maximum variable possible for CONFIG_X86_5LEVEL=y > > configuration to define zsmalloc data structures. > > > > Signed-off-by: Kirill A. Shutemov > > Cc: Minchan Kim > > Cc: Nitin Gupta > > Cc: Sergey Senozhatsky > > --- > > mm/zsmalloc.c | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c > > index 7c38e850a8fc..fe22661f2fe5 100644 > > --- a/mm/zsmalloc.c > > +++ b/mm/zsmalloc.c > > @@ -93,7 +93,13 @@ > > #define MAX_PHYSMEM_BITS BITS_PER_LONG > > #endif > > #endif > > + > > +#ifdef CONFIG_X86_5LEVEL > > +/* MAX_PHYSMEM_BITS is variable, use maximum value here */ > > +#define _PFN_BITS (52 - PAGE_SHIFT) > > +#else > > #define _PFN_BITS (MAX_PHYSMEM_BITS - PAGE_SHIFT) > > +#endif > > This is a totally ugly hack, polluting generic MM code with an x86-ism and an > arbitrary hard-coded constant that would silently lose validity when x86 paging > gets extended again ... Well, yes it's ugly. And I would be glad to find better solution. But I don't see one. And it won't break silently on x86 paging expanding as it won't use CONFIG_X86_5LEVEL, so we would fallback to MAX_PHYSMEM_BITS - PAGE_SHIFT. I worth noting that the code already has x86 hack. See PAE special case for MAX_PHYSMEM_BITS. -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org