From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f71.google.com (mail-pl0-f71.google.com [209.85.160.71]) by kanga.kvack.org (Postfix) with ESMTP id 88EB96B0260 for ; Fri, 29 Dec 2017 03:01:58 -0500 (EST) Received: by mail-pl0-f71.google.com with SMTP id d4so24551776plr.8 for ; Fri, 29 Dec 2017 00:01:58 -0800 (PST) Received: from huawei.com ([45.249.212.35]) by mx.google.com with ESMTPS id s24si27526306plp.220.2017.12.29.00.01.57 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 29 Dec 2017 00:01:57 -0800 (PST) Subject: Re: [RFC patch] ioremap: don't set up huge I/O mappings when p4d/pud/pmd is zero From: Hanjun Guo References: <1514460261-65222-1-git-send-email-guohanjun@huawei.com> Message-ID: <17c8384a-7748-3acc-a56f-78698087560a@huawei.com> Date: Fri, 29 Dec 2017 16:00:25 +0800 MIME-Version: 1.0 In-Reply-To: <1514460261-65222-1-git-send-email-guohanjun@huawei.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: linuxarm@huawei.com, linux-mm@kvack.org, Hanjun Guo , Toshi Kani , Mark Rutland , Will Deacon , Catalin Marinas , Michal Hocko , Andrew Morton , Xuefeng Wang oops, the title of this patch is wrong, should be: ioremap: skip setting up huge I/O mappings when p4d/pud/pmd is zero On 2017/12/28 19:24, Hanjun Guo wrote: > From: Hanjun Guo > > When we using iounmap() to free the 4K mapping, it just clear the PTEs > but leave P4D/PUD/PMD unchanged, also will not free the memory of page > tables. > > This will cause issues on ARM64 platform (not sure if other archs have > the same issue) for this case: > > 1. ioremap a 4K size, valid page table will build, > 2. iounmap it, pte0 will set to 0; > 3. ioremap the same address with 2M size, pgd/pmd is unchanged, > then set the a new value for pmd; > 4. pte0 is leaked; > 5. CPU may meet exception because the old pmd is still in TLB, > which will lead to kernel panic. > > Fix it by skip setting up the huge I/O mappings when p4d/pud/pmd is > zero. > > Reported-by: Lei Li > Signed-off-by: Hanjun Guo > Cc: Toshi Kani > Cc: Mark Rutland > Cc: Will Deacon > Cc: Catalin Marinas > Cc: Michal Hocko > Cc: Andrew Morton > Cc: Xuefeng Wang > --- > > Not sure if this is the right direction, this patch has a obvious > side effect that a mapped address with 4K will not back to 2M. I may > miss something and just wrong, so this is just a RFC version, comments > are welcomed. > > lib/ioremap.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/lib/ioremap.c b/lib/ioremap.c > index b808a39..4e6f19a 100644 > --- a/lib/ioremap.c > +++ b/lib/ioremap.c > @@ -89,7 +89,7 @@ static inline int ioremap_pmd_range(pud_t *pud, unsigned long addr, > do { > next = pmd_addr_end(addr, end); > > - if (ioremap_pmd_enabled() && > + if (ioremap_pmd_enabled() && pmd_none(*pmd) && > ((next - addr) == PMD_SIZE) && > IS_ALIGNED(phys_addr + addr, PMD_SIZE)) { > if (pmd_set_huge(pmd, phys_addr + addr, prot)) > @@ -115,7 +115,7 @@ static inline int ioremap_pud_range(p4d_t *p4d, unsigned long addr, > do { > next = pud_addr_end(addr, end); > > - if (ioremap_pud_enabled() && > + if (ioremap_pud_enabled() && pud_none(*pud) && > ((next - addr) == PUD_SIZE) && > IS_ALIGNED(phys_addr + addr, PUD_SIZE)) { > if (pud_set_huge(pud, phys_addr + addr, prot)) > @@ -141,7 +141,7 @@ static inline int ioremap_p4d_range(pgd_t *pgd, unsigned long addr, > do { > next = p4d_addr_end(addr, end); > > - if (ioremap_p4d_enabled() && > + if (ioremap_p4d_enabled() && p4d_none(*p4d) && > ((next - addr) == P4D_SIZE) && > IS_ALIGNED(phys_addr + addr, P4D_SIZE)) { > if (p4d_set_huge(p4d, phys_addr + addr, prot)) > -- 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