From: Muchun Song <songmuchun@bytedance.com>
To: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: akpm@linux-foundation.org, mike.kravetz@oracle.com,
catalin.marinas@arm.com, will@kernel.org,
tsbogend@alpha.franken.de, James.Bottomley@HansenPartnership.com,
deller@gmx.de, mpe@ellerman.id.au, benh@kernel.crashing.org,
paulus@samba.org, hca@linux.ibm.com, gor@linux.ibm.com,
agordeev@linux.ibm.com, borntraeger@linux.ibm.com,
svens@linux.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org,
davem@davemloft.net, arnd@arndb.de,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org,
linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org,
linux-sh@vger.kernel.org, sparclinux@vger.kernel.org,
linux-arch@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v2 3/3] mm: rmap: Fix CONT-PTE/PMD size hugetlb issue when unmapping
Date: Mon, 9 May 2022 14:42:17 +0800 [thread overview]
Message-ID: <Yni3yTLblEF5aJw5@FVFYT0MHHV2J.usts.net> (raw)
In-Reply-To: <43b11b69e9f0d9d7e7960b86661db27cc404d0c7.1652002221.git.baolin.wang@linux.alibaba.com>
On Sun, May 08, 2022 at 05:36:41PM +0800, Baolin Wang wrote:
> On some architectures (like ARM64), it can support CONT-PTE/PMD size
> hugetlb, which means it can support not only PMD/PUD size hugetlb:
> 2M and 1G, but also CONT-PTE/PMD size: 64K and 32M if a 4K page
> size specified.
>
> When unmapping a hugetlb page, we will get the relevant page table
> entry by huge_pte_offset() only once to nuke it. This is correct
> for PMD or PUD size hugetlb, since they always contain only one
> pmd entry or pud entry in the page table.
>
> However this is incorrect for CONT-PTE and CONT-PMD size hugetlb,
> since they can contain several continuous pte or pmd entry with
> same page table attributes, so we will nuke only one pte or pmd
> entry for this CONT-PTE/PMD size hugetlb page.
>
> And now try_to_unmap() is only passed a hugetlb page in the case
> where the hugetlb page is poisoned. Which means now we will unmap
> only one pte entry for a CONT-PTE or CONT-PMD size poisoned hugetlb
> page, and we can still access other subpages of a CONT-PTE or CONT-PMD
> size poisoned hugetlb page, which will cause serious issues possibly.
>
> So we should change to use huge_ptep_clear_flush() to nuke the
> hugetlb page table to fix this issue, which already considered
> CONT-PTE and CONT-PMD size hugetlb.
>
> We've already used set_huge_swap_pte_at() to set a poisoned
> swap entry for a poisoned hugetlb page. Meanwhile adding a VM_BUG_ON()
> to make sure the passed hugetlb page is poisoned in try_to_unmap().
>
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Thanks.
next prev parent reply other threads:[~2022-05-09 6:48 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-08 9:36 [PATCH v2 0/3] Fix CONT-PTE/PMD size hugetlb issue when unmapping or migrating Baolin Wang
2022-05-08 9:36 ` [PATCH v2 1/3] mm: change huge_ptep_clear_flush() to return the original pte Baolin Wang
2022-05-08 11:09 ` Muchun Song
2022-05-08 13:09 ` Baolin Wang
2022-05-09 4:06 ` Muchun Song
2022-05-09 5:46 ` Christophe Leroy
2022-05-09 8:46 ` Baolin Wang
2022-05-09 20:02 ` Mike Kravetz
2022-05-10 1:35 ` Baolin Wang
2022-05-08 9:36 ` [PATCH v2 2/3] mm: rmap: Fix CONT-PTE/PMD size hugetlb issue when migration Baolin Wang
2022-05-08 12:01 ` kernel test robot
2022-05-08 13:13 ` Baolin Wang
2022-05-08 12:11 ` kernel test robot
2022-05-08 13:31 ` Muchun Song
2022-05-09 21:05 ` Mike Kravetz
2022-05-08 9:36 ` [PATCH v2 3/3] mm: rmap: Fix CONT-PTE/PMD size hugetlb issue when unmapping Baolin Wang
2022-05-09 6:42 ` Muchun Song [this message]
2022-05-09 22:25 ` Mike Kravetz
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