From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 44DDE14C5A1 for ; Tue, 22 Oct 2024 09:10:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729588208; cv=none; b=kXhlRWUapcg4PrwyezPYYrhsgEw8jG1liHsGO1ixI5Sx9WcD9i/EHMLA8n0ygAKA94k12Gsz2ZsZRC/bgoahYZvoBcPTpZMLAuqysh0HDscEOLRlKtOiJHEBiiKowof6b4HQd2XUIry6eoL58j+QXmIprURN8+QYE78Fa/5BSFo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729588208; c=relaxed/simple; bh=KzlVTrdA5Dbq3KetoHWU+wwm2yZXvasu7Aur6guoXFA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gwv3q/vxcajKwuZQBytkQPE0eJsQCUNQ43z5r+Jh9HFt4Bfe74ijIm7hCPy9B4rLHFUoakxM3t2M/asP8zO1e3YwCi/h/kunl1Na3XmdjDPJDKEa2lvkLxnG7B5xhP1QDAhsJfYmOipIDJbU5gN4sDFb4nll2i+SDnE4eoK1wwE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=b529A95H; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="b529A95H" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1729588205; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6atlNrywQf6L1FuctvXZuXYBGuhOpE6LyddYsn3PAm4=; b=b529A95HffTtzEtKfHNBBuBcw2fTJf1BjYVbTW9aC5jnWYSPRnF7x/ED5uoqsPAS3Vgiv0 DaXtU0YsRBuuOSeLmIEr45DVfMbqTYx71hJS1PKNw1A/g9i0ZHXy/XEfjMo/Fqed+HQdtu soPHHBlyqtKi7zlrBoKPWIgfZxuSnG0= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-141-Wicz0LVpMrKSeY-2KDLYTg-1; Tue, 22 Oct 2024 05:10:03 -0400 X-MC-Unique: Wicz0LVpMrKSeY-2KDLYTg-1 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 04C7019560B4; Tue, 22 Oct 2024 09:10:02 +0000 (UTC) Received: from t14s.redhat.com (unknown [10.22.88.114]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 7441319560AE; Tue, 22 Oct 2024 09:09:57 +0000 (UTC) From: David Hildenbrand To: stable@vger.kernel.org Cc: David Hildenbrand , Leo Fu , Thomas Huth , "Matthew Wilcox (Oracle)" , Ryan Roberts , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Hugh Dickins , Kefeng Wang Subject: [PATCH 6.6.y] mm: don't install PMD mappings when THPs are disabled by the hw/process/vma Date: Tue, 22 Oct 2024 11:09:52 +0200 Message-ID: <20241022090952.4101444-1-david@redhat.com> In-Reply-To: <2024101842-empty-espresso-c8a3@gregkh> References: <2024101842-empty-espresso-c8a3@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 We (or rather, readahead logic :) ) might be allocating a THP in the pagecache and then try mapping it into a process that explicitly disabled THP: we might end up installing PMD mappings. This is a problem for s390x KVM, which explicitly remaps all PMD-mapped THPs to be PTE-mapped in s390_enable_sie()->thp_split_mm(), before starting the VM. For example, starting a VM backed on a file system with large folios supported makes the VM crash when the VM tries accessing such a mapping using KVM. Is it also a problem when the HW disabled THP using TRANSPARENT_HUGEPAGE_UNSUPPORTED? At least on x86 this would be the case without X86_FEATURE_PSE. In the future, we might be able to do better on s390x and only disallow PMD mappings -- what s390x and likely TRANSPARENT_HUGEPAGE_UNSUPPORTED really wants. For now, fix it by essentially performing the same check as would be done in __thp_vma_allowable_orders() or in shmem code, where this works as expected, and disallow PMD mappings, making us fallback to PTE mappings. Link: https://lkml.kernel.org/r/20241011102445.934409-3-david@redhat.com Fixes: 793917d997df ("mm/readahead: Add large folio readahead") Signed-off-by: David Hildenbrand Reported-by: Leo Fu Tested-by: Thomas Huth Cc: Thomas Huth Cc: Matthew Wilcox (Oracle) Cc: Ryan Roberts Cc: Christian Borntraeger Cc: Janosch Frank Cc: Claudio Imbrenda Cc: Hugh Dickins Cc: Kefeng Wang Cc: Signed-off-by: Andrew Morton (cherry picked from commit 2b0f922323ccfa76219bcaacd35cd50aeaa13592) Signed-off-by: David Hildenbrand --- Minor contextual difference. Note that the backport of 963756aac1f011d904ddd9548ae82286d3a91f96 is required (send separately as reply to the "FAILED:" mail). --- mm/memory.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/mm/memory.c b/mm/memory.c index b6ddfe22c5d5..742c2f65c2c8 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4293,6 +4293,15 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page) pmd_t entry; vm_fault_t ret = VM_FAULT_FALLBACK; + /* + * It is too late to allocate a small folio, we already have a large + * folio in the pagecache: especially s390 KVM cannot tolerate any + * PMD mappings, but PTE-mapped THP are fine. So let's simply refuse any + * PMD mappings if THPs are disabled. + */ + if (thp_disabled_by_hw() || vma_thp_disabled(vma, vma->vm_flags)) + return ret; + if (!transhuge_vma_suitable(vma, haddr)) return ret; -- 2.46.1