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Fri, 4 Apr 2025 02:19:36 GMT Received: from pps.reinject (localhost [127.0.0.1]) by iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (PPS) with ESMTPS id 45t2pspjer-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 04 Apr 2025 02:19:36 +0000 Received: from iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 5342H8h0030074; Fri, 4 Apr 2025 02:19:35 GMT Received: from localhost.localdomain (ca-dev60.us.oracle.com [10.129.136.27]) by iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (PPS) with ESMTP id 45t2pspj73-13; Fri, 04 Apr 2025 02:19:35 +0000 From: Anthony Yznaga To: akpm@linux-foundation.org, willy@infradead.org, markhemm@googlemail.com, viro@zeniv.linux.org.uk, david@redhat.com, khalid@kernel.org Cc: anthony.yznaga@oracle.com, andreyknvl@gmail.com, dave.hansen@intel.com, luto@kernel.org, brauner@kernel.org, arnd@arndb.de, ebiederm@xmission.com, catalin.marinas@arm.com, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhiramat@kernel.org, rostedt@goodmis.org, vasily.averin@linux.dev, xhao@linux.alibaba.com, pcc@google.com, neilb@suse.de, maz@kernel.org Subject: [PATCH v2 12/20] mm/mshare: prepare for page table sharing support Date: Thu, 3 Apr 2025 19:18:54 -0700 Message-ID: <20250404021902.48863-13-anthony.yznaga@oracle.com> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20250404021902.48863-1-anthony.yznaga@oracle.com> References: <20250404021902.48863-1-anthony.yznaga@oracle.com> MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1095,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-04-04_01,2025-04-03_03,2024-11-22_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 bulkscore=0 mlxscore=0 spamscore=0 adultscore=0 suspectscore=0 mlxlogscore=999 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2502280000 definitions=main-2504040014 X-Proofpoint-ORIG-GUID: kjqCYtOYSi4kyYmM1hlElVfdmwM9mYYd X-Proofpoint-GUID: kjqCYtOYSi4kyYmM1hlElVfdmwM9mYYd X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: EC789160009 X-Stat-Signature: beqie8qhsmks4gziebmugmu185dmn4xy X-Rspam-User: X-HE-Tag: 1743733190-383047 X-HE-Meta: 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 TNcbCV+Y H/d3Zas99Y1wb/mfvsRkjOmMvWLTFQWhCO21CBfGXGdX3LOvXHTcndhZaB6ia+OvbAWlTimJWiOHm50+b0ZPqO5HQP5tQRnPC2keCv9I/tciTeqHwUHzvc+UdrihNkOeWCDHGBkg1Dg7zLeRThCT4ZK21K5PXXl3R2A4T+pE6Dgkf4e0Ce5yRKDZDgyGpcyAtmQ5kxXDxeW6bMEZcCgvcmUXZiplyIdjXtgK5kI8EnmeR4gAZ4Jdu/29Y8RSBLQrrvl54gA93F6tnOPYPmZlUkEc1PIQILzfQBcNtfsiEsgS2DVTb7yCMCx+zUW2m5xX1K3+LLpeyDi0k0to= 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: List-Subscribe: List-Unsubscribe: From: Khalid Aziz In preparation for enabling the handling of page faults in an mshare region provide a way to link an mshare shared page table to a process page table and otherwise find the actual vma in order to handle a page fault. Modify the unmap path to ensure that page tables in mshare regions are unlinked and kept intact when a process exits or an mshare region is explicitly unmapped. Signed-off-by: Khalid Aziz Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Anthony Yznaga --- include/linux/mm.h | 6 +++++ mm/memory.c | 45 +++++++++++++++++++++++++++------ mm/mshare.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 105 insertions(+), 8 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index d6cac2cca4da..f06be2f20c20 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1179,11 +1179,17 @@ static inline bool vma_is_anon_shmem(struct vm_area_struct *vma) { return false; int vma_is_stack_for_current(struct vm_area_struct *vma); #ifdef CONFIG_MSHARE +vm_fault_t find_shared_vma(struct vm_area_struct **vma, unsigned long *addrp); static inline bool vma_is_mshare(const struct vm_area_struct *vma) { return vma->vm_flags & VM_MSHARE; } #else +static inline vm_fault_t find_shared_vma(struct vm_area_struct **vma, unsigned long *addrp) +{ + WARN_ON_ONCE(1); + return VM_FAULT_SIGBUS; +} static inline bool vma_is_mshare(const struct vm_area_struct *vma) { return false; diff --git a/mm/memory.c b/mm/memory.c index db558fe43088..68422b606819 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -247,7 +247,8 @@ static inline void free_pud_range(struct mmu_gather *tlb, p4d_t *p4d, static inline void free_p4d_range(struct mmu_gather *tlb, pgd_t *pgd, unsigned long addr, unsigned long end, - unsigned long floor, unsigned long ceiling) + unsigned long floor, unsigned long ceiling, + bool shared_pud) { p4d_t *p4d; unsigned long next; @@ -259,7 +260,10 @@ static inline void free_p4d_range(struct mmu_gather *tlb, pgd_t *pgd, next = p4d_addr_end(addr, end); if (p4d_none_or_clear_bad(p4d)) continue; - free_pud_range(tlb, p4d, addr, next, floor, ceiling); + if (unlikely(shared_pud)) + p4d_clear(p4d); + else + free_pud_range(tlb, p4d, addr, next, floor, ceiling); } while (p4d++, addr = next, addr != end); start &= PGDIR_MASK; @@ -281,9 +285,10 @@ static inline void free_p4d_range(struct mmu_gather *tlb, pgd_t *pgd, /* * This function frees user-level page tables of a process. */ -void free_pgd_range(struct mmu_gather *tlb, +static void __free_pgd_range(struct mmu_gather *tlb, unsigned long addr, unsigned long end, - unsigned long floor, unsigned long ceiling) + unsigned long floor, unsigned long ceiling, + bool shared_pud) { pgd_t *pgd; unsigned long next; @@ -339,10 +344,17 @@ void free_pgd_range(struct mmu_gather *tlb, next = pgd_addr_end(addr, end); if (pgd_none_or_clear_bad(pgd)) continue; - free_p4d_range(tlb, pgd, addr, next, floor, ceiling); + free_p4d_range(tlb, pgd, addr, next, floor, ceiling, shared_pud); } while (pgd++, addr = next, addr != end); } +void free_pgd_range(struct mmu_gather *tlb, + unsigned long addr, unsigned long end, + unsigned long floor, unsigned long ceiling) +{ + __free_pgd_range(tlb, addr, end, floor, ceiling, false); +} + void free_pgtables(struct mmu_gather *tlb, struct ma_state *mas, struct vm_area_struct *vma, unsigned long floor, unsigned long ceiling, bool mm_wr_locked) @@ -379,9 +391,12 @@ void free_pgtables(struct mmu_gather *tlb, struct ma_state *mas, /* * Optimization: gather nearby vmas into one call down + * + * Do not free the shared page tables of an mshare region. */ while (next && next->vm_start <= vma->vm_end + PMD_SIZE - && !is_vm_hugetlb_page(next)) { + && !is_vm_hugetlb_page(next) + && !vma_is_mshare(next)) { vma = next; next = mas_find(mas, ceiling - 1); if (unlikely(xa_is_zero(next))) @@ -392,9 +407,11 @@ void free_pgtables(struct mmu_gather *tlb, struct ma_state *mas, unlink_file_vma_batch_add(&vb, vma); } unlink_file_vma_batch_final(&vb); - free_pgd_range(tlb, addr, vma->vm_end, - floor, next ? next->vm_start : ceiling); + __free_pgd_range(tlb, addr, vma->vm_end, + floor, next ? next->vm_start : ceiling, + vma_is_mshare(vma)); } + vma = next; } while (vma); } @@ -1884,6 +1901,13 @@ void __unmap_page_range(struct mmu_gather *tlb, pgd_t *pgd; unsigned long next; + /* + * Do not unmap vmas that share page tables through an + * mshare region. + */ + if (vma_is_mshare(vma)) + return; + BUG_ON(addr >= end); tlb_start_vma(tlb, vma); pgd = pgd_offset(vma->vm_mm, addr); @@ -6275,6 +6299,11 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address, if (ret) goto out; + if (unlikely(vma_is_mshare(vma))) { + WARN_ON_ONCE(1); + return VM_FAULT_SIGBUS; + } + if (!arch_vma_access_permitted(vma, flags & FAULT_FLAG_WRITE, flags & FAULT_FLAG_INSTRUCTION, flags & FAULT_FLAG_REMOTE)) { diff --git a/mm/mshare.c b/mm/mshare.c index 792d86c61042..4ddaa0d41070 100644 --- a/mm/mshare.c +++ b/mm/mshare.c @@ -44,6 +44,56 @@ static const struct mmu_notifier_ops mshare_mmu_ops = { .arch_invalidate_secondary_tlbs = mshare_invalidate_tlbs, }; +static p4d_t *walk_to_p4d(struct mm_struct *mm, unsigned long addr) +{ + pgd_t *pgd; + p4d_t *p4d; + + pgd = pgd_offset(mm, addr); + p4d = p4d_alloc(mm, pgd, addr); + if (!p4d) + return NULL; + + return p4d; +} + +/* Returns holding the host mm's lock for read. Caller must release. */ +vm_fault_t +find_shared_vma(struct vm_area_struct **vmap, unsigned long *addrp) +{ + struct vm_area_struct *vma, *guest = *vmap; + struct mshare_data *m_data = guest->vm_private_data; + struct mm_struct *host_mm = m_data->mm; + unsigned long host_addr; + p4d_t *p4d, *guest_p4d; + + mmap_read_lock_nested(host_mm, SINGLE_DEPTH_NESTING); + host_addr = *addrp - guest->vm_start + host_mm->mmap_base; + p4d = walk_to_p4d(host_mm, host_addr); + guest_p4d = walk_to_p4d(guest->vm_mm, *addrp); + if (!p4d_same(*guest_p4d, *p4d)) { + set_p4d(guest_p4d, *p4d); + mmap_read_unlock(host_mm); + return VM_FAULT_NOPAGE; + } + + *addrp = host_addr; + vma = find_vma(host_mm, host_addr); + + /* XXX: expand stack? */ + if (vma && vma->vm_start > host_addr) + vma = NULL; + + *vmap = vma; + + /* + * release host mm lock unless a matching vma is found + */ + if (!vma) + mmap_read_unlock(host_mm); + return 0; +} + static int mshare_vm_op_split(struct vm_area_struct *vma, unsigned long addr) { return -EINVAL; @@ -55,9 +105,21 @@ static int mshare_vm_op_mprotect(struct vm_area_struct *vma, unsigned long start return -EINVAL; } +static void mshare_vm_op_unmap_page_range(struct mmu_gather *tlb, + struct vm_area_struct *vma, + unsigned long addr, unsigned long end, + struct zap_details *details) +{ + /* + * The msharefs vma is being unmapped. Do not unmap pages in the + * mshare region itself. + */ +} + static const struct vm_operations_struct msharefs_vm_ops = { .may_split = mshare_vm_op_split, .mprotect = mshare_vm_op_mprotect, + .unmap_page_range = mshare_vm_op_unmap_page_range, }; /*