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 3EA51197A98 for ; Tue, 22 Oct 2024 09:23:43 +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=1729589025; cv=none; b=W3TW09QzK/j87mjVF1UgcSS3SwEa+SkFIbH0wB07EjLdTCfwvszfxC51BS/elmmkxlPPzovTJFLoKZrwu7ro228DzXGFLzL2TfJj4cRNymUtqPm6aECXXhdk8eNFylrxk0xKOx6PuiU39IyahpZVQISaqLoL+Neul1OtidVKmlk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729589025; c=relaxed/simple; bh=gXvfaI49P46PjRXLj3TVX9vhzBY6AWbniqzGNUIP7hg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UdHYLpB9n5xZF+GLgDdXzEUA6HXtSgQvQQTiqbroGvWoejPdCADnjr5jy5L6m3/swaWRjykut+gD0WEyZcZlMV3OTLkxm/fWf8Kjrxd2d7qSWmVod4tIDj4sSGgjHTln6iZ5LYsixdcqL6y5+jHqWC0kvzX4thonLcjKFZpmTFI= 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=Wx6hM+aK; 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="Wx6hM+aK" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1729589023; 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=f7WhZ/cQlKmFtOCUsHjv6yzC0SlLDEmM96t4pmRbjMg=; b=Wx6hM+aKkEs3xKqA2DSJu4ySSHCTUElJTACjnwiRFFBB3ozKUunScXXxKuePT3EfbLcm6o TEdL2zk99nh3L//Kklaa6qlKRZzBgQmUB0tGR3wC9Et6SNbwlNALpCw88PdSUekpqpb+7u fi5nJ/Uagd7takC4vPMf7i1qwtSWW4k= Received: from mx-prod-mc-05.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-627-_XgqDPE0OJK_PAQrXpXd_g-1; Tue, 22 Oct 2024 05:23:40 -0400 X-MC-Unique: _XgqDPE0OJK_PAQrXpXd_g-1 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 85C921955F68; Tue, 22 Oct 2024 09:23:38 +0000 (UTC) Received: from t14s.redhat.com (unknown [10.22.88.114]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 420121956046; Tue, 22 Oct 2024 09:23:35 +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 6.1.y] mm: don't install PMD mappings when THPs are disabled by the hw/process/vma Date: Tue, 22 Oct 2024 11:23:33 +0200 Message-ID: <20241022092333.4127283-1-david@redhat.com> In-Reply-To: <2024101837-mammogram-headsman-2dec@gregkh> References: <2024101837-mammogram-headsman-2dec@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 10.30.177.12 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 da9fed5e6025..d0af31ffd6b5 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4328,6 +4328,15 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page) int i; 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