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Thu, 19 Mar 2020 03:56:30 +0000 Received: from b01ledav004.gho.pok.ibm.com (b01ledav004.gho.pok.ibm.com [9.57.199.109]) by b01cxnp23032.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 02J3uU2Q48824670 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 19 Mar 2020 03:56:30 GMT Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 20FBF11206D; Thu, 19 Mar 2020 03:56:30 +0000 (GMT) Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B7F1511206B; Thu, 19 Mar 2020 03:56:26 +0000 (GMT) Received: from skywalker.ibmuc.com (unknown [9.199.34.213]) by b01ledav004.gho.pok.ibm.com (Postfix) with ESMTP; Thu, 19 Mar 2020 03:56:26 +0000 (GMT) From: "Aneesh Kumar K.V" To: linuxppc-dev@lists.ozlabs.org, mpe@ellerman.id.au, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org Cc: npiggin@gmail.com, paulus@ozlabs.org, leonardo@linux.ibm.com, kirill@shutemov.name, "Aneesh Kumar K.V" Subject: [PATCH v2 03/22] powerpc/mm/hash64: use _PAGE_PTE when checking for pte_present Date: Thu, 19 Mar 2020 09:25:50 +0530 Message-Id: <20200319035609.158654-4-aneesh.kumar@linux.ibm.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200319035609.158654-1-aneesh.kumar@linux.ibm.com> References: <20200319035609.158654-1-aneesh.kumar@linux.ibm.com> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.645 definitions=2020-03-18_10:2020-03-18,2020-03-18 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 impostorscore=0 malwarescore=0 suspectscore=0 mlxlogscore=999 priorityscore=1501 mlxscore=0 bulkscore=0 lowpriorityscore=0 spamscore=0 clxscore=1015 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003190015 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: This makes the pte_present check stricter by checking for additional _PAG= E_PTE bit. A level 1 pte pointer (THP pte) can be switched to a pointer to leve= l 0 pte page table page by following two operations. 1) THP split. 2) madvise(MADV_DONTNEED) in parallel to page fault. A lockless page table walk need to make sure we can handle such changes gracefully. Signed-off-by: Aneesh Kumar K.V --- arch/powerpc/include/asm/book3s/64/pgtable.h | 15 ++++++++++----- arch/powerpc/mm/book3s64/hash_utils.c | 11 +++++++++-- 2 files changed, 19 insertions(+), 7 deletions(-) diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/= include/asm/book3s/64/pgtable.h index 201a69e6a355..89eb7b350df8 100644 --- a/arch/powerpc/include/asm/book3s/64/pgtable.h +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h @@ -553,6 +553,12 @@ static inline pte_t pte_clear_savedwrite(pte_t pte) } #endif /* CONFIG_NUMA_BALANCING */ =20 +static inline bool pte_hw_valid(pte_t pte) +{ + return (pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT | _PAGE_PTE)) =3D=3D + cpu_to_be64(_PAGE_PRESENT | _PAGE_PTE); +} + static inline int pte_present(pte_t pte) { /* @@ -561,12 +567,11 @@ static inline int pte_present(pte_t pte) * invalid during ptep_set_access_flags. Hence we look for _PAGE_INVALI= D * if we find _PAGE_PRESENT cleared. */ - return !!(pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT | _PAGE_INVALID)); -} =20 -static inline bool pte_hw_valid(pte_t pte) -{ - return !!(pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT)); + if (pte_hw_valid(pte)) + return true; + return (pte_raw(pte) & cpu_to_be64(_PAGE_INVALID | _PAGE_PTE)) =3D=3D + cpu_to_be64(_PAGE_INVALID | _PAGE_PTE); } =20 #ifdef CONFIG_PPC_MEM_KEYS diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book= 3s64/hash_utils.c index 8530ddbba56f..e2a7873c7760 100644 --- a/arch/powerpc/mm/book3s64/hash_utils.c +++ b/arch/powerpc/mm/book3s64/hash_utils.c @@ -1349,8 +1349,15 @@ int hash_page_mm(struct mm_struct *mm, unsigned lo= ng ea, goto bail; } =20 - /* Add _PAGE_PRESENT to the required access perm */ - access |=3D _PAGE_PRESENT; + /* + * Add _PAGE_PRESENT to the required access perm. If there are parallel + * updates to the pte that can possibly clear _PAGE_PTE, catch that too= . + * + * We can safely use the return pte address in rest of the function + * because we do set H_PAGE_BUSY which prevents further updates to pte + * from generic code. + */ + access |=3D _PAGE_PRESENT | _PAGE_PTE; =20 /* * Pre-check access permissions (will be re-checked atomically --=20 2.24.1