From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757524Ab3AOPXg (ORCPT ); Tue, 15 Jan 2013 10:23:36 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:29714 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756606Ab3AOPXf (ORCPT ); Tue, 15 Jan 2013 10:23:35 -0500 Date: Tue, 15 Jan 2013 10:22:54 -0500 From: Konrad Rzeszutek Wilk To: Stefano Stabellini Cc: Yinghai Lu , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , "Eric W. Biederman" , Andrew Morton , Borislav Petkov , Jan Kiszka , Jason Wessel , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v7u1 10/31] x86, 64bit: Don't set max_pfn_mapped wrong value early on native path Message-ID: <20130115152254.GC2682@phenom.dumpdata.com> References: <1357260531-11115-1-git-send-email-yinghai@kernel.org> <1357260531-11115-11-git-send-email-yinghai@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: acsinet22.oracle.com [141.146.126.238] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 15, 2013 at 01:48:45PM +0000, Stefano Stabellini wrote: > On Fri, 4 Jan 2013, Yinghai Lu wrote: > > We are not having max_pfn_mapped set correctly until init_memory_mapping. > > > > so don't print it initial value for 64bit > > > > Also need to use KERNEL_IMAGE_SIZE directly for highmap cleanup. > > > > Signed-off-by: Yinghai Lu > > --- > > arch/x86/kernel/head64.c | 3 --- > > arch/x86/kernel/setup.c | 2 ++ > > arch/x86/mm/init_64.c | 6 +++++- > > 3 files changed, 7 insertions(+), 4 deletions(-) > > > > diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c > > index a3fc233..7061d8b 100644 > > --- a/arch/x86/kernel/head64.c > > +++ b/arch/x86/kernel/head64.c > > @@ -146,9 +146,6 @@ void __init x86_64_start_kernel(char * real_mode_data) > > /* clear bss before set_intr_gate with early_idt_handler */ > > clear_bss(); > > > > - /* XXX - this is wrong... we need to build page tables from scratch */ > > - max_pfn_mapped = KERNEL_IMAGE_SIZE >> PAGE_SHIFT; > > - > > for (i = 0; i < NUM_EXCEPTION_VECTORS; i++) { > > #ifdef CONFIG_EARLY_PRINTK > > set_intr_gate(i, &early_idt_handlers[i]); > > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c > > index 63160c6..04797e78 100644 > > --- a/arch/x86/kernel/setup.c > > +++ b/arch/x86/kernel/setup.c > > @@ -910,8 +910,10 @@ void __init setup_arch(char **cmdline_p) > > setup_bios_corruption_check(); > > #endif > > > > +#ifdef CONFIG_X86_32 > > printk(KERN_DEBUG "initial memory mapped: [mem 0x00000000-%#010lx]\n", > > (max_pfn_mapped< > +#endif > > > > reserve_real_mode(); > > > > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c > > index 9c5f2b1..98385a2 100644 > > --- a/arch/x86/mm/init_64.c > > +++ b/arch/x86/mm/init_64.c > > @@ -394,10 +394,14 @@ void __init init_extra_mapping_uc(unsigned long phys, unsigned long size) > > void __init cleanup_highmap(void) > > { > > unsigned long vaddr = __START_KERNEL_map; > > - unsigned long vaddr_end = __START_KERNEL_map + (max_pfn_mapped << PAGE_SHIFT); > > + unsigned long vaddr_end = __START_KERNEL_map + KERNEL_IMAGE_SIZE; > > unsigned long end = roundup((unsigned long)_brk_end, PMD_SIZE) - 1; > > pmd_t *pmd = level2_kernel_pgt; > > > > + /* Xen has its own end somehow with abused max_pfn_mapped */ > > + if (max_pfn_mapped) > > + vaddr_end = __START_KERNEL_map + (max_pfn_mapped << PAGE_SHIFT); > > If you are going to put a comment like that in the code, could you > please at least add some useful details, rather than a generic > "somehow"? It doesn't seem very helpful to me or to any other hackers > looking at the code. Hm I think I actually pointed out to him in the previous reviews how we alter it and that he should ingest some of those comments in this patch. > > The issue is even described as a comment in the code at the beginning of > arch/x86/xen/mmu.c:xen_setup_kernel_pagetable: > > /* max_pfn_mapped is the last pfn mapped in the initial memory > * mappings. Considering that on Xen after the kernel mappings we > * have the mappings of some pages that don't exist in pfn space, we > * set max_pfn_mapped to the last real pfn mapped. */ > > Now if max_pfn_mapped is supposed to represent the last pfn mapped in > the initial memory mapping, then I think that the way Xen uses > max_pfn_mapped is actually correct. > > > The question is: has max_pfn_mapped actually changed meaning? > Because if it hasn't I don't see why you need this change. > > > > > for (; vaddr + PMD_SIZE - 1 < vaddr_end; pmd++, vaddr += PMD_SIZE) { > > if (pmd_none(*pmd)) > > continue; > > -- > > 1.7.10.4 > > > > -- > > 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/ > >