From mboxrd@z Thu Jan 1 00:00:00 1970 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 27266CEBF61 for ; Mon, 17 Nov 2025 11:47:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8A41D8E002C; Mon, 17 Nov 2025 06:46:59 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 87BD48E0003; Mon, 17 Nov 2025 06:46:59 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7B9098E002C; Mon, 17 Nov 2025 06:46:59 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 6A00E8E0003 for ; Mon, 17 Nov 2025 06:46:59 -0500 (EST) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 2E18E8A028 for ; Mon, 17 Nov 2025 11:46:59 +0000 (UTC) X-FDA: 84119922558.20.140E225 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf16.hostedemail.com (Postfix) with ESMTP id 948FA18000B for ; Mon, 17 Nov 2025 11:46:57 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="Rf/8XkGu"; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf16.hostedemail.com: domain of rppt@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=rppt@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1763380017; a=rsa-sha256; cv=none; b=wmJBf+7aOmeS+MhesrpWJK6fEFQkFSxLvIchDlNAmep0PmKEJsiyDGKvxoLANIW4K4eMVB Anl3KQF9R78oxH5yXcH+NjR0Wjcelmox605hNVumW7L1p617I7xfX9uwuOi1QzJmfYIddB xfa3XPp6dzu2OWpMh3wFK6GTooT1DTg= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="Rf/8XkGu"; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf16.hostedemail.com: domain of rppt@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=rppt@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1763380017; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=jfuD4/wM6iC83CYIumcwxFHRVOHtnx9THrGQgJmC4Aw=; b=UnhaNhdNhxIHWxJ3frzkev7qW0u/QQEsJGev6drDHBiIEBR8375U35mzhs6nTa5pOUYMHQ vHpGkUMU6ksKUe5LfLKLEPXpU6v6yoOU0ONcltkRGyr8Azu6ZhBZl+zLzeuhrA0e3l+SlB kGsqqxGl+X89cX7sUuGd+QS0+oi5RwM= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 1E7F6601F9; Mon, 17 Nov 2025 11:46:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DC696C19424; Mon, 17 Nov 2025 11:46:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763380016; bh=tJnQnmAt6Wvr+31OW1+YrQRyI6HqICukDnZlnmjRypc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Rf/8XkGuM+tcAn7TrAR0d2+5u5uqFi1D2E8h6j3T7SAafDrHya+wVSKsW2gDh1b5y K2+2fvSNEgBJHtSSo8PvpHFVe0MRhtZLUgUDyM5oiLcdphrXC9eA/jZDjbPZAaTrRo rDSRA5Fyu+Mc6vvW0F485NTJQU5MHTAXSiDwm8yfmUXEags6P5SK3CBc6Bq3cLDWM1 x3SoyKBJLLxA5hA/COB0/KXlRKgglY6gJt1CaBK5SHXRz5JwsqEW3ruUzmlPsYRe4g rCHLAeIKpe0YthRimRzIIgMr1b2m69ExF0wnE+iXlAn+vU8WTSITB0irmna3kmD7K1 20YszAdK1urcw== From: Mike Rapoport To: linux-mm@kvack.org Cc: Andrea Arcangeli , Andrew Morton , Baolin Wang , David Hildenbrand , Hugh Dickins , "Liam R. Howlett" , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Nikita Kalyazin , Paolo Bonzini , Peter Xu , Sean Christopherson , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [RFC PATCH 3/4] userfaultfd, guest_memfd: support userfault minor mode in guest_memfd Date: Mon, 17 Nov 2025 13:46:30 +0200 Message-ID: <20251117114631.2029447-4-rppt@kernel.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20251117114631.2029447-1-rppt@kernel.org> References: <20251117114631.2029447-1-rppt@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 948FA18000B X-Stat-Signature: 666ys77y68zwip6bpff5psimtfp4e36h X-HE-Tag: 1763380017-435357 X-HE-Meta: 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 zvEy9UiO pnIjKx8pVromkh/ov1VQGBbM9iioj6tbvMy+4KhzgCapaN22CV6rLD8OseGpS0BQpm4f4as5M7fCCAhLkdS56teNYk5jObCHXA6KaFBapxBlszfQ3VK1gwmKn022v1PKF6qi0k8er3X5DFvnr2OEIzxBBDzY9pnTYiJ6ec8w3P8N0Zk5t4o+JXWltQYoZ377xnCx4xp7zOrKjuQnYUdI8/DX+1wAvNPJbPcIIXhjWMDyErrRks+LfFs1zgy0yJ9ivE+gsb+d/7Yx9qMaejp0T4Ckj/g== 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: "Mike Rapoport (Microsoft)" * Export handle_userfault() for KVM module so that fault() handler in guest_memfd would be able to notify userspace about page faults in its address space. * Implement get_pagecache_folio() for guest_memfd. * And finally, introduce UFFD_FEATURE_MINOR_GENERIC that will allow using userfaultfd minor mode with memory types other than shmem and hugetlb provided they are allowed to call handle_userfault() and implement get_pagecache_folio(). Signed-off-by: Mike Rapoport (Microsoft) --- fs/userfaultfd.c | 4 +++- include/uapi/linux/userfaultfd.h | 8 +++++++- virt/kvm/guest_memfd.c | 30 ++++++++++++++++++++++++++++++ 3 files changed, 40 insertions(+), 2 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 54c6cc7fe9c6..964fa2662d5c 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -537,6 +537,7 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason) out: return ret; } +EXPORT_SYMBOL_FOR_MODULES(handle_userfault, "kvm"); static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, struct userfaultfd_wait_queue *ewq) @@ -1978,7 +1979,8 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx, uffdio_api.features = UFFD_API_FEATURES; #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR uffdio_api.features &= - ~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM); + ~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM | + UFFD_FEATURE_MINOR_GENERIC); #endif #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP; diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h index 2841e4ea8f2c..c5cbd4a5a26e 100644 --- a/include/uapi/linux/userfaultfd.h +++ b/include/uapi/linux/userfaultfd.h @@ -42,7 +42,8 @@ UFFD_FEATURE_WP_UNPOPULATED | \ UFFD_FEATURE_POISON | \ UFFD_FEATURE_WP_ASYNC | \ - UFFD_FEATURE_MOVE) + UFFD_FEATURE_MOVE | \ + UFFD_FEATURE_MINOR_GENERIC) #define UFFD_API_IOCTLS \ ((__u64)1 << _UFFDIO_REGISTER | \ (__u64)1 << _UFFDIO_UNREGISTER | \ @@ -210,6 +211,10 @@ struct uffdio_api { * UFFD_FEATURE_MINOR_SHMEM indicates the same support as * UFFD_FEATURE_MINOR_HUGETLBFS, but for shmem-backed pages instead. * + * UFFD_FEATURE_MINOR_GENERIC indicates that minor faults can be + * intercepted for file-backed memory in case subsystem backing this + * memory supports it. + * * UFFD_FEATURE_EXACT_ADDRESS indicates that the exact address of page * faults would be provided and the offset within the page would not be * masked. @@ -248,6 +253,7 @@ struct uffdio_api { #define UFFD_FEATURE_POISON (1<<14) #define UFFD_FEATURE_WP_ASYNC (1<<15) #define UFFD_FEATURE_MOVE (1<<16) +#define UFFD_FEATURE_MINOR_GENERIC (1<<17) __u64 features; __u64 ioctls; diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index fbca8c0972da..5e3c63307fdf 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -4,6 +4,7 @@ #include #include #include +#include #include "kvm_mm.h" @@ -369,6 +370,12 @@ static vm_fault_t kvm_gmem_fault_user_mapping(struct vm_fault *vmf) return vmf_error(err); } + if (userfaultfd_minor(vmf->vma)) { + folio_unlock(folio); + folio_put(folio); + return handle_userfault(vmf, VM_UFFD_MINOR); + } + if (WARN_ON_ONCE(folio_test_large(folio))) { ret = VM_FAULT_SIGBUS; goto out_folio; @@ -390,8 +397,31 @@ static vm_fault_t kvm_gmem_fault_user_mapping(struct vm_fault *vmf) return ret; } +#ifdef CONFIG_USERFAULTFD +static struct folio *kvm_gmem_get_pagecache_folio(struct vm_area_struct *vma, + pgoff_t pgoff) +{ + struct inode *inode = file_inode(vma->vm_file); + struct folio *folio; + + folio = kvm_gmem_get_folio(inode, pgoff); + if (IS_ERR_OR_NULL(folio)) + return folio; + + if (!folio_test_uptodate(folio)) { + clear_highpage(folio_page(folio, 0)); + kvm_gmem_mark_prepared(folio); + } + + return folio; +} +#endif + static const struct vm_operations_struct kvm_gmem_vm_ops = { .fault = kvm_gmem_fault_user_mapping, +#ifdef CONFIG_USERFAULTFD + .get_pagecache_folio = kvm_gmem_get_pagecache_folio, +#endif }; static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma) -- 2.50.1