From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 8D41D5383F8; Tue, 29 Sep 2026 15:14:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790694855; cv=none; b=FtR/iWn7KN3Z7SVFXPjUXEjo7kkObYp+MpWl8j6yxIifhSGzAVv9x/eMJ47Onai+xL1PXJ3++2UcTLSjgiQ75NdoAugIrNg5GGwTLf0NXcPS6Tc741Of4zarWU61+Q+tQA3VFK/WxYlk5ISKLxRMWmc7szgstQBHikw5kwBXC+U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790694855; c=relaxed/simple; bh=XEtGGorji3NtkUx1Ni1j3Vf8MbEwOxKvWSr7f1Dxavo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lwXyrFY4tCrfeUTDx8u/1isCdlcp1nYeadcZuiIjwQF4chwy+4hrnFBEmCkKGTXYGA9/m7xiXhyOvfzYcA7qt7hAAgQ5ybTgrLyusKieWor5aXp9tKpwVS03vPrUn4QsYRhITxAgeJwW6ikKNgTtfUd2E+FwP/sYf78+7NDJbAg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=EfBvsUkU; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=VFjjYzNh; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="EfBvsUkU"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="VFjjYzNh" Date: Tue, 29 Sep 2026 17:14:01 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1790694843; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=pkQpYFiMxSAX1DzMvKY2lHJd+Uw2ccGZnZL7SuyrGMY=; b=EfBvsUkUz4qh+/XUVEPUlvuwAyW7wbF7E8uDLnTyznKk2n4rsH5/IVXa/H5Sp9kYt27TmQ Bu2IK+yy4dMQ7sh38j9m1ef1ftagXFU6MjIo2CMUQuW2Pr6PYka1E99Bp7CIZkTSA/Eoui fq/cMZPvEc26JYKhe2/1NCiAY9OVF3uSNlDkQgGa+XJyIWcAvWNpTiPPIg57j9D+QcOB1A 7XPjbY1aVlJZTh8adcwDUw+9AGp9qgORO2T2w9GCQl9LeVNtoh+8jclbQrzCGBnzpMfWdJ RqFD58cMxM6UkL2sSq3Uz+qML61ntsxXadYO/6U/mz5drfeTQ7nzVAsOg7Yddg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1790694843; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=pkQpYFiMxSAX1DzMvKY2lHJd+Uw2ccGZnZL7SuyrGMY=; b=VFjjYzNhNXdMOYOJdjTGaz3xpdUVT/yPc+R1E41OoqhTIHdrpWfHY65AGjhV4AI4PgRCEN gsW+CqRESCX/b0Cw== From: Sebastian Andrzej Siewior To: Ard Biesheuvel Cc: Prashant Singh , Jeremy Kerr , Clark Williams , Steven Rostedt , Jonathan Corbet , Shuah Khan , Randy Dunlap , "Luis Claudio R. Goncalves" , Steve McIntyre <93sam@debian.org>, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-rt-devel@lists.linux.dev Subject: Re: [PATCH v4] efivarfs: add nostatfs mount option to skip QueryVariableInfo() Message-ID: <20260929151401.doOQX7D0@linutronix.de> References: <20260928203445.72318-1-singhpra@juniper.net> <20260929074312.v3jT8uel@linutronix.de> <59d5452c-42b1-4784-a593-5e549a2a0f12@app.fastmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <59d5452c-42b1-4784-a593-5e549a2a0f12@app.fastmail.com> On 2026-09-29 14:22:31 [+0200], Ard Biesheuvel wrote: > Hi Sebastian, Hi Ard, > Thanks for taking a look. doing my best=E2=80=A6 > >> --- a/fs/efivarfs/internal.h > >> +++ b/fs/efivarfs/internal.h > >> @@ -11,6 +11,7 @@ > >> struct efivarfs_mount_opts { > >> kuid_t uid; > >> kgid_t gid; > >> + bool nostatfs; /* skip QueryVariableInfo() in statfs() */ > > Here and below you add a comment to every change you make. What about > > focusing on the important parts, that deserve an explanation why a > > change has been made. For instance why nostatfs has the READ_ONCE/ > > WRITE_ONCE accessors and sometimes it does not. > > >=20 > AIUI the READ_ONCE/WRITE_ONCE were added because Sashiko warned about > potential KCSAN splats? It would be nice to mention that. :) > In any case, KCSAN is runtime instrumentation, and efi_reboot_required() > is only called after all other CPUs have been brought down. So if anythin= g, > this should just wrap the read on the reboot path in a data_race() so > that we don't trigger any instrumentation inadvertently on the way down. Right. So if anything, there could be a data_race() in one place instead inconsistent READ/ WRITE once as we have it now. Sebastian