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 9B3CA1FBCBC; Wed, 6 Nov 2024 12:55:11 +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=1730897711; cv=none; b=ZYfqopKQkF+lbOyA+BguTExAjeCXWvuBAGP+FbvCZ7/FLNepR9lKRlP+HmDxFbqdAoOp85HrF2oTT9jYiOQxzFdrzGcm445u6Gb977FcyY/S1RxzsxPg4mqS8Ns1nIMa2epA7We1ePFItYBcsROZTQxT98LS7iCyKvFUKZXskbI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730897711; c=relaxed/simple; bh=2NyOVKEx2qr7yKhRPYOtZq2yFrDAVH2ccsDeXaH5GCk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PdnKLivBXZ80lhV2iNvgWpt1gUV1snD+ek5b3CBl4mvcFdKarYt1tvNRHn4+6FoOLOVEnkjKPOeQmBwYa732VOmorAwHOV+7ACn2WBTGXEEAo1o9uczgfkCxSi3bNrWKd/ETqLEbqJGTlu5ODTkYKhhfkwK+mprgdSA5kyeG41s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ZOSef5D2; 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="ZOSef5D2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E766FC4CECD; Wed, 6 Nov 2024 12:55:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1730897711; bh=2NyOVKEx2qr7yKhRPYOtZq2yFrDAVH2ccsDeXaH5GCk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZOSef5D2Axu11A4Pd6P2MWAOd/s0eQoa2oyZkDRsFGDBJdNH1Bp42Ea2X/2sgOlQP 9PXufVA34jF6bWTsh8C2ss1eNM/KuF6c+IrinjZzPaAHM1QAqcqnFLDgRhWnLk1zix a1iTSdz26w7VVELxXNpmImAKsIY5p2mLYuGZ5Pb4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, David Hildenbrand , Leo Fu , Thomas Huth , "Matthew Wilcox (Oracle)" , Ryan Roberts , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Hugh Dickins , Kefeng Wang , Andrew Morton Subject: [PATCH 6.6 144/151] mm: dont install PMD mappings when THPs are disabled by the hw/process/vma Date: Wed, 6 Nov 2024 13:05:32 +0100 Message-ID: <20241106120312.811917353@linuxfoundation.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241106120308.841299741@linuxfoundation.org> References: <20241106120308.841299741@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Hildenbrand commit 2b0f922323ccfa76219bcaacd35cd50aeaa13592 upstream. 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 Signed-off-by: David Hildenbrand Signed-off-by: Greg Kroah-Hartman --- mm/memory.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/mm/memory.c +++ b/mm/memory.c @@ -4293,6 +4293,15 @@ vm_fault_t do_set_pmd(struct vm_fault *v 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;