From patchwork Tue Oct 12 01:17:26 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mina Almasry X-Patchwork-Id: 12551257 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BA822C433F5 for ; Tue, 12 Oct 2021 01:17:33 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 39C1760F21 for ; Tue, 12 Oct 2021 01:17:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 39C1760F21 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id A22FD6B006C; Mon, 11 Oct 2021 21:17:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9D1456B0071; Mon, 11 Oct 2021 21:17:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8722D900002; Mon, 11 Oct 2021 21:17:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 770A06B006C for ; Mon, 11 Oct 2021 21:17:32 -0400 (EDT) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 3C31431E5E for ; Tue, 12 Oct 2021 01:17:32 +0000 (UTC) X-FDA: 78686022744.12.A793817 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) by imf19.hostedemail.com (Postfix) with ESMTP id E53FBB0020BA for ; Tue, 12 Oct 2021 01:17:31 +0000 (UTC) Received: by mail-yb1-f202.google.com with SMTP id s66-20020a252c45000000b005ba35261459so24868410ybs.7 for ; Mon, 11 Oct 2021 18:17:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:cc; bh=bGbpyFsi1zCs9YQDf5XQdvwqdaD2wirD+A7f9Qi/V9s=; b=XuPCK1Kswix6uy4jS2XUDLxMRAEHDKsvkpUFAigO2xyhxtH7i26jffNR4xZTEW0ULN chhVFGQ/4IuGOV+lh8wsJTak451mpG3JGQvPifQ4i2VhRfY1TccCzhXj4U4JwydBFiOk Am5ugyRxJmwlBvf5i1A34Fg8v5+wHR6n1vL7o9Xr7sTMlQXbyYYTHpJlX9T0E+zpIFFw js2jDzgDBWegfY+FQW8kFV1PVYRRpiuv2JlXQwnB+q3QvTt4axwg97VPPQQxarkAj4mI yUd2L0F0KJbbzxfFmKhAmOstXnLPMdZKqu2Rmllyi6DRQ0qlz4jOsGrynpyJwDH1Py/g Vvmw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:cc; bh=bGbpyFsi1zCs9YQDf5XQdvwqdaD2wirD+A7f9Qi/V9s=; b=o0w0FQ1rDuinHd2y0h8z2HYmIWtN3xrhrkeJfK7eN0jz0Yydy2sJSzg4O1wU8Lu0gz tLIdt0VdUnVktTNMfW4ldZraKWTnsiTNw7Gu0UV8jLPf7vlRqrfk08JAg2sl2ngN8NxI Ol2ctexm1f6j9Uv2HFvgPBdfXEU5ivMEH1zatAaShQ1eLv2gxZCRD/btKt/xaVzAJOhm hrPrrgNZSg+MHM01DriM3HUBAyTcbzZFgLDmVlerrOo1MZ+BfgSzFRTHB3lXS10h0uag hkrfTQIbT7IPAFZW8jI90yEjQUR2/tzvSC0edAfz3wiDUAs2G2FdqSI+AaC+hQiKepJi TwSw== X-Gm-Message-State: AOAM5325vJ1v6sN08sx1qxIYnu8z2GHv3SBS+zm7jW56s7pT3WA83lVI M1cEjIB5WVKXP7T7U3ynBhUn6BFebNno8X2rMA== X-Google-Smtp-Source: ABdhPJyvxgqPo4Es9a7HNhaYBFtdGlvqui4Kwhur0Jik+9b4nQHGtL12M4Ek2rVFBOl+ejnbgtuE3aHK4QqXV9LkRw== X-Received: from almasrymina.svl.corp.google.com ([2620:15c:2cd:202:62d9:8583:862e:cb1d]) (user=almasrymina job=sendgmr) by 2002:a25:b309:: with SMTP id l9mr24284908ybj.188.1634001451084; Mon, 11 Oct 2021 18:17:31 -0700 (PDT) Date: Mon, 11 Oct 2021 18:17:26 -0700 Message-Id: <20211012011728.646120-1-almasrymina@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.33.0.882.g93a45727a2-goog Subject: [PATCH v6 1/2] mm, hugepages: add mremap() support for hugepage backed vma From: Mina Almasry Cc: Mina Almasry , Mike Kravetz , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Ken Chen , Chris Kennelly , Michal Hocko , Vlastimil Babka , Kirill Shutemov X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: E53FBB0020BA X-Stat-Signature: upjcogb155iyj363ntu11jz1x5tenmpz Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=XuPCK1Ks; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf19.hostedemail.com: domain of 3K-JkYQsKCJQy9AyGFMA6By4CC492.0CA96BIL-AA8Jy08.CF4@flex--almasrymina.bounces.google.com designates 209.85.219.202 as permitted sender) smtp.mailfrom=3K-JkYQsKCJQy9AyGFMA6By4CC492.0CA96BIL-AA8Jy08.CF4@flex--almasrymina.bounces.google.com X-HE-Tag: 1634001451-627875 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: Support mremap() for hugepage backed vma segment by simply repositioning page table entries. The page table entries are repositioned to the new virtual address on mremap(). Hugetlb mremap() support is of course generic; my motivating use case is a library (hugepage_text), which reloads the ELF text of executables in hugepages. This significantly increases the execution performance of said executables. Restricts the mremap operation on hugepages to up to the size of the original mapping as the underlying hugetlb reservation is not yet capable of handling remapping to a larger size. During the mremap() operation we detect pmd_share'd mappings and we unshare those during the mremap(). On access and fault the sharing is established again. Signed-off-by: Mina Almasry Cc: Mike Kravetz Cc: Andrew Morton Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org Cc: Ken Chen Cc: Chris Kennelly Cc: Michal Hocko Cc: Vlastimil Babka Cc: Kirill Shutemov Reviewed-by: Mike Kravetz --- Changes in v6: - Converted hugetlb_vma_shareable() to static only (fixes build warning). - Removed huge_pmd_shared(). It's not needed since I removed the BUG_ON(huge_pmd_shared) in v3. - Removed *...* format for emphasis. - Fixed mremap behavior to hugepage-align lengths but return error if addresses are not hugepage aligned. Changes in v5: - Remove hugetlb_vma_shareable and huge_pmd_shared dummy definitions for !CONFIG_HUGETLB_PAGE config, since they are not used and were causing added warning and build errors. Changes in v4: - Added addr, new_addr, old_len, and new_len hugepage alignment. Changes in v3: - Addressed review comments from Mike. - Separated tests into their own patch. Changes in v2: - Re-wrote comment around clear_vma_resv_huge_pages() to make it clear that the resv_map has been moved to the new VMA and why we need to clear it from the current VMA. - We detect huge_pmd_shared() pte's and unshare those rather than bug on hugetlb_vma_shareable(). - This case now returns EFAULT: if (!vma || vma->vm_start > addr) goto out; - Added kselftests for mremap() support. --- include/linux/hugetlb.h | 15 ++++++ mm/hugetlb.c | 116 +++++++++++++++++++++++++++++++++++++--- mm/mremap.c | 36 +++++++++++-- 3 files changed, 156 insertions(+), 11 deletions(-) -- 2.33.0.882.g93a45727a2-goog diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index ebaba02706c87..c6b70f1ede6bf 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -124,6 +124,7 @@ struct hugepage_subpool *hugepage_new_subpool(struct hstate *h, long max_hpages, void hugepage_put_subpool(struct hugepage_subpool *spool); void reset_vma_resv_huge_pages(struct vm_area_struct *vma); +void clear_vma_resv_huge_pages(struct vm_area_struct *vma); int hugetlb_sysctl_handler(struct ctl_table *, int, void *, size_t *, loff_t *); int hugetlb_overcommit_handler(struct ctl_table *, int, void *, size_t *, loff_t *); @@ -132,6 +133,10 @@ int hugetlb_treat_movable_handler(struct ctl_table *, int, void *, size_t *, int hugetlb_mempolicy_sysctl_handler(struct ctl_table *, int, void *, size_t *, loff_t *); +int move_hugetlb_page_tables(struct vm_area_struct *vma, + struct vm_area_struct *new_vma, + unsigned long old_addr, unsigned long new_addr, + unsigned long len); int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *, struct vm_area_struct *); long follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *, struct page **, struct vm_area_struct **, @@ -215,6 +220,10 @@ static inline void reset_vma_resv_huge_pages(struct vm_area_struct *vma) { } +static inline void clear_vma_resv_huge_pages(struct vm_area_struct *vma) +{ +} + static inline unsigned long hugetlb_total_pages(void) { return 0; @@ -262,6 +271,12 @@ static inline int copy_hugetlb_page_range(struct mm_struct *dst, return 0; } +#define move_hugetlb_page_tables(vma, new_vma, old_addr, new_addr, len) \ + ({ \ + BUG(); \ + 0; \ + }) + static inline void hugetlb_report_meminfo(struct seq_file *m) { } diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 6d2f4c25dd9fb..6e91cd3905e73 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1015,6 +1015,35 @@ void reset_vma_resv_huge_pages(struct vm_area_struct *vma) vma->vm_private_data = (void *)0; } +/* + * Reset and decrement one ref on hugepage private reservation. + * Called with mm->mmap_sem writer semaphore held. + * This function should be only used by move_vma() and operate on + * same sized vma. It should never come here with last ref on the + * reservation. + */ +void clear_vma_resv_huge_pages(struct vm_area_struct *vma) +{ + /* + * Clear the old hugetlb private page reservation. + * It has already been transferred to new_vma. + * + * During a mremap() operation of a hugetlb vma we call move_vma() + * which copies vma into new_vma and unmaps vma. After the copy + * operation both new_vma and vma share a reference to the resv_map + * struct, and at that point vma is about to be unmapped. We don't + * want to return the reservation to the pool at unmap of vma because + * the reservation still lives on in new_vma, so simply decrement the + * ref here and remove the resv_map reference from this vma. + */ + struct resv_map *reservations = vma_resv_map(vma); + + if (reservations && is_vma_resv_set(vma, HPAGE_RESV_OWNER)) + kref_put(&reservations->refs, resv_map_release); + + reset_vma_resv_huge_pages(vma); +} + /* Returns true if the VMA has associated reserve pages */ static bool vma_has_reserves(struct vm_area_struct *vma, long chg) { @@ -4800,6 +4829,82 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, return ret; } +static void move_huge_pte(struct vm_area_struct *vma, unsigned long old_addr, + unsigned long new_addr, pte_t *src_pte) +{ + struct hstate *h = hstate_vma(vma); + struct mm_struct *mm = vma->vm_mm; + pte_t *dst_pte, pte; + spinlock_t *src_ptl, *dst_ptl; + + dst_pte = huge_pte_offset(mm, new_addr, huge_page_size(h)); + dst_ptl = huge_pte_lock(h, mm, dst_pte); + src_ptl = huge_pte_lockptr(h, mm, src_pte); + + /* + * We don't have to worry about the ordering of src and dst ptlocks + * because exclusive mmap_sem (or the i_mmap_lock) prevents deadlock. + */ + if (src_ptl != dst_ptl) + spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); + + pte = huge_ptep_get_and_clear(mm, old_addr, src_pte); + set_huge_pte_at(mm, new_addr, dst_pte, pte); + + if (src_ptl != dst_ptl) + spin_unlock(src_ptl); + spin_unlock(dst_ptl); +} + +int move_hugetlb_page_tables(struct vm_area_struct *vma, + struct vm_area_struct *new_vma, + unsigned long old_addr, unsigned long new_addr, + unsigned long len) +{ + struct hstate *h = hstate_vma(vma); + struct address_space *mapping = vma->vm_file->f_mapping; + unsigned long sz = huge_page_size(h); + struct mm_struct *mm = vma->vm_mm; + unsigned long old_end = old_addr + len; + unsigned long old_addr_copy; + pte_t *src_pte, *dst_pte; + struct mmu_notifier_range range; + + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm, old_addr, + old_end); + adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end); + mmu_notifier_invalidate_range_start(&range); + /* Prevent race with file truncation */ + i_mmap_lock_write(mapping); + for (; old_addr < old_end; old_addr += sz, new_addr += sz) { + src_pte = huge_pte_offset(mm, old_addr, sz); + if (!src_pte) + continue; + if (huge_pte_none(huge_ptep_get(src_pte))) + continue; + + /* old_addr arg to huge_pmd_unshare() is a pointer and so the + * arg may be modified. Pass a copy instead to preserve the + * value in old_arg. + */ + old_addr_copy = old_addr; + + if (huge_pmd_unshare(mm, vma, &old_addr_copy, src_pte)) + continue; + + dst_pte = huge_pte_alloc(mm, new_vma, new_addr, sz); + if (!dst_pte) + break; + + move_huge_pte(vma, old_addr, new_addr, src_pte); + } + i_mmap_unlock_write(mapping); + flush_tlb_range(vma, old_end - len, old_end); + mmu_notifier_invalidate_range_end(&range); + + return len + old_addr - old_end; +} + static void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma, unsigned long start, unsigned long end, struct page *ref_page) @@ -6280,7 +6385,8 @@ static unsigned long page_table_shareable(struct vm_area_struct *svma, return saddr; } -static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr) +static bool hugetlb_vma_shareable(struct vm_area_struct *vma, + unsigned long addr) { unsigned long base = addr & PUD_MASK; unsigned long end = base + PUD_SIZE; @@ -6299,7 +6405,7 @@ bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr) if (uffd_disable_huge_pmd_share(vma)) return false; #endif - return vma_shareable(vma, addr); + return hugetlb_vma_shareable(vma, addr); } /* @@ -6339,12 +6445,6 @@ void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, * sharing is possible. For hugetlbfs, this prevents removal of any page * table entries associated with the address space. This is important as we * are setting up sharing based on existing page table entries (mappings). - * - * NOTE: This routine is only called from huge_pte_alloc. Some callers of - * huge_pte_alloc know that sharing is not possible and do not take - * i_mmap_rwsem as a performance optimization. This is handled by the - * if !vma_shareable check at the beginning of the routine. i_mmap_rwsem is - * only required for subsequent processing. */ pte_t *huge_pmd_share(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr, pud_t *pud) diff --git a/mm/mremap.c b/mm/mremap.c index c0b6c41b7b78f..002eec83e91e5 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -489,6 +489,10 @@ unsigned long move_page_tables(struct vm_area_struct *vma, old_end = old_addr + len; flush_cache_range(vma, old_addr, old_end); + if (is_vm_hugetlb_page(vma)) + return move_hugetlb_page_tables(vma, new_vma, old_addr, + new_addr, len); + mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma, vma->vm_mm, old_addr, old_end); mmu_notifier_invalidate_range_start(&range); @@ -646,6 +650,10 @@ static unsigned long move_vma(struct vm_area_struct *vma, mremap_userfaultfd_prep(new_vma, uf); } + if (is_vm_hugetlb_page(vma)) { + clear_vma_resv_huge_pages(vma); + } + /* Conceal VM_ACCOUNT so old reservation is not undone */ if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) { vma->vm_flags &= ~VM_ACCOUNT; @@ -739,9 +747,6 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr, (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))) return ERR_PTR(-EINVAL); - if (is_vm_hugetlb_page(vma)) - return ERR_PTR(-EINVAL); - /* We can't remap across vm area boundaries */ if (old_len > vma->vm_end - addr) return ERR_PTR(-EFAULT); @@ -937,6 +942,31 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, if (mmap_write_lock_killable(current->mm)) return -EINTR; + vma = find_vma(mm, addr); + if (!vma || vma->vm_start > addr) { + ret = EFAULT; + goto out; + } + + if (is_vm_hugetlb_page(vma)) { + struct hstate *h __maybe_unused = hstate_vma(vma); + + old_len = ALIGN(old_len, huge_page_size(h)); + new_len = ALIGN(new_len, huge_page_size(h)); + + /* addrs must be huge page aligned */ + if (addr & ~huge_page_mask(h)) + goto out; + if (new_addr & ~huge_page_mask(h)) + goto out; + + /* + * Don't allow remap expansion, because the underlying hugetlb + * reservation is not yet capable to handle split reservation. + */ + if (new_len > old_len) + goto out; + } if (flags & (MREMAP_FIXED | MREMAP_DONTUNMAP)) { ret = mremap_to(addr, old_len, new_addr, new_len, From patchwork Tue Oct 12 01:17:27 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mina Almasry X-Patchwork-Id: 12551259 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B6A25C433EF for ; Tue, 12 Oct 2021 01:17:36 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4665C60273 for ; Tue, 12 Oct 2021 01:17:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 4665C60273 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id D090C6B0071; 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Mon, 11 Oct 2021 18:17:34 -0700 (PDT) Date: Mon, 11 Oct 2021 18:17:27 -0700 In-Reply-To: <20211012011728.646120-1-almasrymina@google.com> Message-Id: <20211012011728.646120-2-almasrymina@google.com> Mime-Version: 1.0 References: <20211012011728.646120-1-almasrymina@google.com> X-Mailer: git-send-email 2.33.0.882.g93a45727a2-goog Subject: [PATCH v6 2/2] mm, hugepages: Add hugetlb vma mremap() test From: Mina Almasry Cc: Mina Almasry , Mike Kravetz , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Ken Chen , Chris Kennelly , Michal Hocko , Vlastimil Babka , Kirill Shutemov X-Rspamd-Queue-Id: DD962103DD1D X-Stat-Signature: yr9zu5n5o4t1oegaaiaoc6d5ct4g5ozd Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=lff8HcPi; spf=pass (imf13.hostedemail.com: domain of 3LuJkYQsKCJc1CD1JIPD9E17FF7C5.3FDC9ELO-DDBM13B.FI7@flex--almasrymina.bounces.google.com designates 209.85.219.201 as permitted sender) smtp.mailfrom=3LuJkYQsKCJc1CD1JIPD9E17FF7C5.3FDC9ELO-DDBM13B.FI7@flex--almasrymina.bounces.google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspamd-Server: rspam06 X-HE-Tag: 1634001454-644229 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: Signed-off-by: Mina Almasry Cc: Mike Kravetz Cc: Andrew Morton Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org Cc: Ken Chen Cc: Chris Kennelly Cc: Michal Hocko Cc: Vlastimil Babka Cc: Kirill Shutemov --- Changes in v6: - Reverted change in v4: test case now passes huge page aligned addrs to mmap/mremap. Changes in v4: - Added comments to make test output clearer. - Modified test case slightly to test hugepage alignment of new_addr. --- tools/testing/selftests/vm/.gitignore | 1 + tools/testing/selftests/vm/Makefile | 1 + tools/testing/selftests/vm/hugepage-mremap.c | 165 +++++++++++++++++++ 3 files changed, 167 insertions(+) create mode 100644 tools/testing/selftests/vm/hugepage-mremap.c -- 2.33.0.882.g93a45727a2-goog diff --git a/tools/testing/selftests/vm/.gitignore b/tools/testing/selftests/vm/.gitignore index b02eac613fdda..2e7e86e852828 100644 --- a/tools/testing/selftests/vm/.gitignore +++ b/tools/testing/selftests/vm/.gitignore @@ -1,5 +1,6 @@ # SPDX-License-Identifier: GPL-2.0-only hugepage-mmap +hugepage-mremap hugepage-shm khugepaged map_hugetlb diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile index d9605bd10f2de..1607322a112c9 100644 --- a/tools/testing/selftests/vm/Makefile +++ b/tools/testing/selftests/vm/Makefile @@ -29,6 +29,7 @@ TEST_GEN_FILES = compaction_test TEST_GEN_FILES += gup_test TEST_GEN_FILES += hmm-tests TEST_GEN_FILES += hugepage-mmap +TEST_GEN_FILES += hugepage-mremap TEST_GEN_FILES += hugepage-shm TEST_GEN_FILES += khugepaged TEST_GEN_FILES += madv_populate diff --git a/tools/testing/selftests/vm/hugepage-mremap.c b/tools/testing/selftests/vm/hugepage-mremap.c new file mode 100644 index 0000000000000..e84b79922fe6e --- /dev/null +++ b/tools/testing/selftests/vm/hugepage-mremap.c @@ -0,0 +1,165 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * hugepage-mremap: + * + * Example of remapping huge page memory in a user application using the + * mremap system call. Before running this application, make sure that the + * administrator has mounted the hugetlbfs filesystem (on some directory + * like /mnt) using the command mount -t hugetlbfs nodev /mnt. In this + * example, the app is requesting memory of size 10MB that is backed by + * huge pages. + * + */ + +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include /* Definition of O_* constants */ +#include /* Definition of SYS_* constants */ +#include +#include +#include + +#define LENGTH (1UL * 1024 * 1024 * 1024) + +#define PROTECTION (PROT_READ | PROT_WRITE | PROT_EXEC) +#define FLAGS (MAP_SHARED | MAP_ANONYMOUS) + +static void check_bytes(char *addr) +{ + printf("First hex is %x\n", *((unsigned int *)addr)); +} + +static void write_bytes(char *addr) +{ + unsigned long i; + + for (i = 0; i < LENGTH; i++) + *(addr + i) = (char)i; +} + +static int read_bytes(char *addr) +{ + unsigned long i; + + check_bytes(addr); + for (i = 0; i < LENGTH; i++) + if (*(addr + i) != (char)i) { + printf("Mismatch at %lu\n", i); + return 1; + } + return 0; +} + +static void register_region_with_uffd(char *addr, size_t len) +{ + long uffd; /* userfaultfd file descriptor */ + struct uffdio_api uffdio_api; + struct uffdio_register uffdio_register; + + /* Create and enable userfaultfd object. */ + + uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK); + if (uffd == -1) { + perror("userfaultfd"); + exit(1); + } + + uffdio_api.api = UFFD_API; + uffdio_api.features = 0; + if (ioctl(uffd, UFFDIO_API, &uffdio_api) == -1) { + perror("ioctl-UFFDIO_API"); + exit(1); + } + + /* Create a private anonymous mapping. The memory will be + * demand-zero paged--that is, not yet allocated. When we + * actually touch the memory, it will be allocated via + * the userfaultfd. + */ + + addr = mmap(NULL, len, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (addr == MAP_FAILED) { + perror("mmap"); + exit(1); + } + + printf("Address returned by mmap() = %p\n", addr); + + /* Register the memory range of the mapping we just created for + * handling by the userfaultfd object. In mode, we request to track + * missing pages (i.e., pages that have not yet been faulted in). + */ + + uffdio_register.range.start = (unsigned long)addr; + uffdio_register.range.len = len; + uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING; + if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register) == -1) { + perror("ioctl-UFFDIO_REGISTER"); + exit(1); + } +} + +int main(void) +{ + int ret = 0; + + int fd = open("/mnt/huge/test", O_CREAT | O_RDWR, 0755); + + if (fd < 0) { + perror("Open failed"); + exit(1); + } + + /* mmap to a PUD aligned address to hopefully trigger pmd sharing. */ + unsigned long suggested_addr = 0x7eaa40000000; + void *haddr = mmap((void *)suggested_addr, LENGTH, PROTECTION, + MAP_HUGETLB | MAP_SHARED | MAP_POPULATE, fd, 0); + printf("Map haddr: Returned address is %p\n", haddr); + if (haddr == MAP_FAILED) { + perror("mmap1"); + exit(1); + } + + /* mmap again to a dummy address to hopefully trigger pmd sharing. */ + suggested_addr = 0x7daa40000000; + void *daddr = mmap((void *)suggested_addr, LENGTH, PROTECTION, + MAP_HUGETLB | MAP_SHARED | MAP_POPULATE, fd, 0); + printf("Map daddr: Returned address is %p\n", daddr); + if (daddr == MAP_FAILED) { + perror("mmap3"); + exit(1); + } + + suggested_addr = 0x7faa40000000; + void *vaddr = + mmap((void *)suggested_addr, LENGTH, PROTECTION, FLAGS, -1, 0); + printf("Map vaddr: Returned address is %p\n", vaddr); + if (vaddr == MAP_FAILED) { + perror("mmap2"); + exit(1); + } + + register_region_with_uffd(haddr, LENGTH); + + void *addr = mremap(haddr, LENGTH, LENGTH, + MREMAP_MAYMOVE | MREMAP_FIXED, vaddr); + if (addr == MAP_FAILED) { + perror("mremap"); + exit(1); + } + + printf("Mremap: Returned address is %p\n", addr); + check_bytes(addr); + write_bytes(addr); + ret = read_bytes(addr); + + munmap(addr, LENGTH); + + return ret; +}