From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 A918215445B for ; Fri, 18 Oct 2024 08:26:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729240004; cv=none; b=D3aQ7xx1Dfc5g6v2dfiXU1dQDV22fqdLgxOQ6HWs25Ei46GS8oorS37ZklRJP9DcUd0k/Ml3lqN/6WNPZvxDSSgLjqG+95e7JfmT99+Lu/Bnsbeaz7JEwIRH6hvWkK4HV7ofkLArkSiPQ0JpHOOBCZwDiQHa4vR3VREyLkpORqM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729240004; c=relaxed/simple; bh=wci6fe4axmFU8+4QKLAt36NvQa04HAGAdHfI4rbwJeY=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=FaIhm4aAuWRUDmN2JVl6Q1p7xrVrcttVAbEDzqLjl7m3k1HTh3fBq/fW7JB4m/a54o7G+M0mPyDouEdVHDqnZr58by8Y0nN38Myckj6+M38HpRMToane8+t7Tsyy1AaOZAwMxmbrHL/Bbkv4rZ+VeLztdmHmsh5hGA9Kzc+HZcg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=SNgW8BM1; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="SNgW8BM1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BAF02C4CEC3; Fri, 18 Oct 2024 08:26:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1729240004; bh=wci6fe4axmFU8+4QKLAt36NvQa04HAGAdHfI4rbwJeY=; h=Subject:To:Cc:From:Date:From; b=SNgW8BM1BLebnfMT+1xkT4oDMZFoDPN61Yi52QVXK2dTaiQV6vTUXPowOzk/rKN8t BMkdoAfwbsM055l0Xm2f354PGBPcvylKY1xtF7Pw0VeGN7fojc5AVEk/FKuzKj7cC2 KzxPdz6ly4ot6KfLEiSrDa4vl1TRN3SSnxjyTzh0= Subject: FAILED: patch "[PATCH] mm: don't install PMD mappings when THPs are disabled by the" failed to apply to 6.11-stable tree To: david@redhat.com,akpm@linux-foundation.org,bfu@redhat.com,borntraeger@linux.ibm.com,frankja@linux.ibm.com,hughd@google.com,imbrenda@linux.ibm.com,ryan.roberts@arm.com,stable@vger.kernel.org,thuth@redhat.com,wangkefeng.wang@huawei.com,willy@infradead.org Cc: From: Date: Fri, 18 Oct 2024 10:26:41 +0200 Message-ID: <2024101841-keep-coma-4963@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.11-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.11.y git checkout FETCH_HEAD git cherry-pick -x 2b0f922323ccfa76219bcaacd35cd50aeaa1359 # git commit -s git send-email --to '' --in-reply-to '2024101841-keep-coma-4963@gregkh' --subject-prefix 'PATCH 6.11.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 2b0f922323ccfa76219bcaacd35cd50aeaa13592 Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Fri, 11 Oct 2024 12:24:45 +0200 Subject: [PATCH] mm: don't install PMD mappings when THPs are disabled by the hw/process/vma 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 diff --git a/mm/memory.c b/mm/memory.c index c0869a962ddd..30feedabc932 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4920,6 +4920,15 @@ 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 (!thp_vma_suitable_order(vma, haddr, PMD_ORDER)) return ret;