From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3vkjvb2NZBzDqYd for ; Fri, 17 Mar 2017 09:34:35 +1100 (AEDT) Date: Fri, 17 Mar 2017 09:19:20 +1100 From: Paul Mackerras To: "Aneesh Kumar K.V" Cc: benh@kernel.crashing.org, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH V2 06/11] powerpc/mm/hugetlb: Filter out hugepage size not supported by page table layout Message-ID: <20170316221920.GF10100@fergus.ozlabs.ibm.com> References: <1489660329-22501-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1489660329-22501-7-git-send-email-aneesh.kumar@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1489660329-22501-7-git-send-email-aneesh.kumar@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, Mar 16, 2017 at 04:02:04PM +0530, Aneesh Kumar K.V wrote: > Without this if firmware reports 1MB page size support we will crash > trying to use 1MB as hugetlb page size. > > echo 300 > /sys/kernel/mm/hugepages/hugepages-1024kB/nr_hugepages > > kernel BUG at ./arch/powerpc/include/asm/hugetlb.h:19! > ..... > .... > [c0000000e2c27b30] c00000000029dae8 .hugetlb_fault+0x638/0xda0 > [c0000000e2c27c30] c00000000026fb64 .handle_mm_fault+0x844/0x1d70 > [c0000000e2c27d70] c00000000004805c .do_page_fault+0x3dc/0x7c0 > [c0000000e2c27e30] c00000000000ac98 handle_page_fault+0x10/0x30 > > With fix, we don't enable 1MB as hugepage size. > > bash-4.2# cd /sys/kernel/mm/hugepages/ > bash-4.2# ls > hugepages-16384kB hugepages-16777216kB > > Signed-off-by: Aneesh Kumar K.V > --- > arch/powerpc/mm/hugetlbpage.c | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c > index 8c3389cbcd12..eb8d42bac00b 100644 > --- a/arch/powerpc/mm/hugetlbpage.c > +++ b/arch/powerpc/mm/hugetlbpage.c > @@ -738,6 +738,7 @@ static int __init add_huge_page_size(unsigned long long size) > int shift = __ffs(size); > int mmu_psize; > > +#ifndef CONFIG_PPC_BOOK3S_64 This #ifndef doesn't really seem necessary. All it is removing is a check for size <= PAGE_SIZE. Yes that check is subsumed by the checks you are adding below, but on the other hand, #if[n]defs inside functions are ugly and make the code harder to read. Since this is not a hot path, let's not have the ifndef. > /* Check that it is a page size supported by the hardware and > * that it fits within pagetable and slice limits. */ > if (size <= PAGE_SIZE) > @@ -749,10 +750,29 @@ static int __init add_huge_page_size(unsigned long long size) > if (!is_power_of_2(size) || (shift > SLICE_HIGH_SHIFT)) > return -EINVAL; > #endif > +#endif /* CONFIG_PPC_BOOK3S_64 */ > > if ((mmu_psize = shift_to_mmu_psize(shift)) < 0) > return -EINVAL; > > +#ifdef CONFIG_PPC_BOOK3S_64 > + /* > + * We need to make sure that for different page sizes reported by > + * firmware we only add hugetlb support for page sizes that can be > + * supported by linux page table layout. > + * For now we have > + * Radix: 2M > + * Hash: 16M and 16G > + */ > + if (radix_enabled()) { > + if (mmu_psize != MMU_PAGE_2M) > + return -EINVAL; > + } else { > + if (mmu_psize != MMU_PAGE_16M && mmu_psize != MMU_PAGE_16G) > + return -EINVAL; > + } > +#endif > + > BUG_ON(mmu_psize_defs[mmu_psize].shift != shift); > > /* Return if huge page size has already been setup */ > -- > 2.7.4 Paul.