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 3639F25D1F2; Fri, 28 Feb 2025 10:07:24 +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=1740737245; cv=none; b=SThY4lPouDkE5UoZinRQ4LHDL1jGNo+oL1G+xSjcokP/unTaHRTbLqhUF0JFPeSoU61oEzHWkUq3wd3eS9VrIRySQRKpMLoyVPL2aAn1XvSNe3fzajCDvxCJ2NP44lks/ZOddkuC2msAs+DBwhZ7EgXznDljM0xs0L6OXHfHV4w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740737245; c=relaxed/simple; bh=x1cKyeaIVIgjeWHsX5Z1LYYOPIaS5AKHdehywA2BHHQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=hs+ZqBm4U431+lqvfCTvKcFp1i/sHMrrHCR3cWbiuk2WNW4rpRkmTFovXvKdJ6jLyHyAHDGRxTTvUkC/OFH9Zf9qJyPnMg99SpXps3jr2NbH60KJw9yqI5sBJmw8x/1STkJSpCMacjU8TZkIC7hYwcXaQz6aQGPFbkUKWdGP8Jo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XhW8r5hn; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="XhW8r5hn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 05BBCC4CED6; Fri, 28 Feb 2025 10:07:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1740737244; bh=x1cKyeaIVIgjeWHsX5Z1LYYOPIaS5AKHdehywA2BHHQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XhW8r5hn+jBRN7HvPYUlH40MsOgOmOm343ImfzpHgNR0Xck2w+kaXCw0yenhDOl+c nYbRUuSdOj9ddawGAappMhqu5layPUbl/FD72QW+rKGp5ebJ5c0KE1CZTZUBLDZQAv JSkXZGZZsHCNHiQGuT5T4LwqlUgqACRrizL6uc07ymY64Jat/sjc17XhDQeNxZkmGd UDHYdqeVybNHhj8XqhEuMXCmyaeXrCciT8KGR4/qxbqr1xdvTHzFN+0QjDSHTw4w1Z V92e2G1VEvCwwDb/N0MB7N5+ToSNV03xhXxiwPPEMfN70N6O/L62ckDc3psemfOtxE CBwCfY3W2x+7g== Date: Fri, 28 Feb 2025 11:07:19 +0100 From: Ingo Molnar To: Brendan Jackman Cc: Jonathan Corbet , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 0/3] x86/cpu: Add facility to force-enable CPU caps and bugs Message-ID: References: <20241220-force-cpu-bug-v2-0-7dc71bce742a@google.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: * Brendan Jackman wrote: > Hi folks, happy new year. I hope this ping isn't too aggressive given > the season - please let me know if it is. > > Any new thoughts on this? Sorry, this series got lost in the holiday season (apparently you weren't nearly pushy enough to breach the maintainer patch-detection noise/signal level :-), and this functionality is definitely useful and the series looks good to me. Integration with clearcpuid= is so much more generic than the original variant and reuses a lot of that logic, so that's a big plus. I've applied it to the x86 tree under the tip:x86/cpu branch and if everything goes fine in testing it should hit v6.15 in a couple of weeks. One additional thing - which I'd suggest we make a 4th patch, because it affects the existing clearcpuid= behavior - is to extend set/clearcpuid= with a bit more boot time verbosity, right now it taints the kernel: /* empty-string, i.e., ""-defined feature flags */ if (!x86_cap_flags[bit]) pr_cont(" " X86_CAP_FMT_NUM, x86_cap_flag_num(bit)); else pr_cont(" " X86_CAP_FMT, x86_cap_flag(bit)); if (set) setup_force_cpu_cap(bit); else setup_clear_cpu_cap(bit); taint++; I'd suggest we do what PeterZ suggested back in December: in addition to the tainting, also emit an informative pr_warn() for every CPU feature bit enabled/disabled over what was present, and maybe make a bit of a distinction between 'feature' and 'bug' feature bits. Thanks, Ingo