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 179B529BD9D; Tue, 12 Aug 2025 19:27:55 +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=1755026875; cv=none; b=GyhVMr9qsPQDw6KH7tF9cOAJiBnbN8OBrJfaxZpZ8M5bhMgu5CfpJ7lUy6iCr/XU5ho6XPR2eCF0gYbyTfedCmHw3+M+wrtxu2ILc8ZG6nXVD+X4/J7NDMt3ox5a7DXOlFPfmHiuYHyGnLxKcenOoLxIR8p4eMrDosASVE1f7co= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755026875; c=relaxed/simple; bh=Z0OAZlpab9KAWMoU2zKotmeBTACGrOuYGmS3quvF7L0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=KfKv4UBuUzH8bVaqMzviXcPC011fI0rOXNgFDy8nmHnjBWbYlh3OcMxom4GLoXBQXZdUnB8i/Gmd6LMwAFE9BP3OkV9ExEPvH1uUyM/esfiQmnU20wBH41aYHn+Xd5mjFwqJvfsED9yFxwS/d8HCs5IkABEHsxamlelqbh9oYso= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=H+54gK5t; 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="H+54gK5t" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 610ABC4CEF0; Tue, 12 Aug 2025 19:27:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1755026875; bh=Z0OAZlpab9KAWMoU2zKotmeBTACGrOuYGmS3quvF7L0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=H+54gK5t5cmdGu/MajPypBOpezPntWFzVu+XyBF+rhO/MMvLcMVFgVuLwWrmiHzwM n8m/OvgsVnQojKMpVLQ6cWn4exhiiQ4SZ0Yu21BK8XupeObvqpqcULsY0txjzMRzru ruahq2vo9kUkqDY31xqQKfuf6ee6vX2a57pagIdo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Alexander Gordeev , Claudio Imbrenda , Gerald Schaefer Subject: [PATCH 6.15 465/480] s390/mm: Remove possible false-positive warning in pte_free_defer() Date: Tue, 12 Aug 2025 19:51:13 +0200 Message-ID: <20250812174416.569473373@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250812174357.281828096@linuxfoundation.org> References: <20250812174357.281828096@linuxfoundation.org> User-Agent: quilt/0.68 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 6.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gerald Schaefer commit 5647f61ad9171e8f025558ed6dc5702c56a33ba3 upstream. Commit 8211dad627981 ("s390: add pte_free_defer() for pgtables sharing page") added a warning to pte_free_defer(), on our request. It was meant to warn if this would ever be reached for KVM guest mappings, because the page table would be freed w/o a gmap_unlink(). THP mappings are not allowed for KVM guests on s390, so this should never happen. However, it is possible that the warning is triggered in a valid case as false-positive. s390_enable_sie() takes the mmap_lock, marks all VMAs as VM_NOHUGEPAGE and splits possibly existing THP guest mappings. mm->context.has_pgste is set to 1 before that, to prevent races with the mm_has_pgste() check in MADV_HUGEPAGE. khugepaged drops the mmap_lock for file mappings and might run in parallel, before a vma is marked VM_NOHUGEPAGE, but after mm->context.has_pgste was set to 1. If it finds file mappings to collapse, it will eventually call pte_free_defer(). This will trigger the warning, but it is a valid case because gmap is not yet set up, and the THP mappings will be split again. Therefore, remove the warning and the comment. Fixes: 8211dad627981 ("s390: add pte_free_defer() for pgtables sharing page") Cc: # 6.6+ Reviewed-by: Alexander Gordeev Reviewed-by: Claudio Imbrenda Signed-off-by: Gerald Schaefer Signed-off-by: Alexander Gordeev Signed-off-by: Greg Kroah-Hartman --- arch/s390/mm/pgalloc.c | 5 ----- 1 file changed, 5 deletions(-) --- a/arch/s390/mm/pgalloc.c +++ b/arch/s390/mm/pgalloc.c @@ -176,11 +176,6 @@ void pte_free_defer(struct mm_struct *mm struct ptdesc *ptdesc = virt_to_ptdesc(pgtable); call_rcu(&ptdesc->pt_rcu_head, pte_free_now); - /* - * THPs are not allowed for KVM guests. Warn if pgste ever reaches here. - * Turn to the generic pte_free_defer() version once gmap is removed. - */ - WARN_ON_ONCE(mm_has_pgste(mm)); } #endif /* CONFIG_TRANSPARENT_HUGEPAGE */