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 2AC2927991E; Wed, 25 Feb 2026 14:32:47 +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=1772029968; cv=none; b=OG+T4QnftMoLPp8N+X6yc9dogBRScdzu1kJKZk6w0MvZPWu4RzYFYnSInKJUYYt3v81Mz6xFJoja3ouqj+IH6RXiudntgrId4VLPQshSkp2omvI+1pqHX8vt/XSTBSAjVB3760dWZ3fKorpV+09QV3rwVdMhtpepQ4pUp76RLi8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772029968; c=relaxed/simple; bh=gdf8pBnOXBOpOoKt0PEusZ3Be9PkpcMHkXIHvimakX0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=F62Pex1b+qpX7jxlqifa+jbYow7aYFEOkXFYCap9xoUMSjQhPU9tHBW9LCnhKoShVGainqoojztJQ1tOpvrFFDkHFevvPGGMlf6eVFrD1XWy21Ii1zb6T7x5EZBfJTWnKVJcs1G7tOohM7MkYTYF6He37NrhWjkGy1c5CIGfsZ4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=WzNRPSlb; 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="WzNRPSlb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9F7A8C116D0; Wed, 25 Feb 2026 14:32:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1772029967; bh=gdf8pBnOXBOpOoKt0PEusZ3Be9PkpcMHkXIHvimakX0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WzNRPSlbtwEYeX+MNyA/mE9OD29JpppNgF8GAcAfmsLH1BGZjR/yffWOV6dj+YjAR bZW/q0bigJwSk2cdUa37QHt7fbHGQ6XXtZvkXIEXnEeUvWTUmyFy0GfZN93/zsLRQi AEb9QNIlbbj4f3YV2TH/z/LdH1EUSRb2vVKbQrQU= Date: Wed, 25 Feb 2026 06:32:40 -0800 From: Greg KH To: Shung-Hsi Yu Cc: Harshit Mogalapalli , Ricardo =?iso-8859-1?Q?B=2E_Marli=E8re?= , stable@vger.kernel.org, Shuah Khan , linux-kselftest@vger.kernel.org, Daniel Borkmann , Alexei Starovoitov , Andrii Nakryiko , bpf@vger.kernel.org Subject: Re: Latest BPF selftests on stable kernels (was 'Re: [PATCH stable 6.12 0/5] Backport selftest for "bpf: Check skb->transport_header is set in bpf_skb_check_mtu"') Message-ID: <2026022557-synapse-schilling-e88b@gregkh> References: <20260224073810.85945-1-shung-hsi.yu@suse.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed, Feb 25, 2026 at 10:35:06AM +0800, Shung-Hsi Yu wrote: > Cc BPF mailing list and maintainers. Plus other in the referenced > thread. > > Hi Harshit, > > On Tue, Feb 24, 2026 at 09:18:04AM -0300, Ricardo B. Marlière wrote: > > On Tue Feb 24, 2026 at 4:53 AM -03, Harshit Mogalapalli wrote: > > > On 24/02/26 13:08, Shung-Hsi Yu wrote: > > >> This patchset backport the corresponding BPF selftests for commit > > >> d946f3c98328 ("bpf: Check skb->transport_header is set in > > >> bpf_skb_check_mtu"), which has already been included since 6.12.63. > > >> > > >> The BPF selftest added in commit 6cc73f35406c ("selftests/bpf: Test > > >> bpf_skb_check_mtu(BPF_MTU_CHK_SEGS) when transport_header is not set") > > >> additionally depends on network namespace support for BPF selftests > > >> added by Bastien, otherwise the MTU in root networking namespace will be > > >> set to 10, causing other BPF selftests to fail. Credit goes to Ricardo > > >> Marlière for figuring out the dependency. > > > > > > Note: > > > I have recently learnt that ideally we are supposed to run upstream > > > latest kselftests on stable kernels as well. If a feature is not > > > supported the kselftests are meant to be skipped. > > Thanks you for the bringing this up! This was also mentioned by Daniel > (Borkmann), but my experience aligns with Ricardo's. > > > That is not true for BPF, from my (limited) experience. > > I do want running latest BPF selftests to work on stable thought, made > some half-hearted attempts last April on trying bpf-next's BPF selftests > (during 6.15 phase) run on stable/linux-6.14.y, but wasn't able to get > pass the building phase. > > As far as I remember I ran into issue building bpf_testmod.ko (kernel > module) of bpf-next against 6.14, and other similar issues related data > structure or API changes. Pretty much the same set of problems we get > when trying to build any driver in the latest kernel against stable > kernels. > > Maybe it can work if BPF selftests that does not depends on > bpf_testmod.ko, and build failures of BPF programs are simply ignored > (not sure how feasible that is, probably would make Makefile much > complicated), so for now I'm sticking with backporting BPF selftests to > stable kernels. If a kernel test module is involved, then yes, you are right, those changes do need to be backported as mix/match of kernel modules to other trees is not something that we support. We only want this to be the rule for when we have purely userspace test cases/code. thanks, greg k-h