From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 23FC72C11F1; Mon, 29 Jun 2026 22:46:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782773195; cv=none; b=SAiPAONBheJi3JURc5BWJPBS+dHK0rKtwsYmhBSJONWIwLyTY8k/ZAMTWf0W7pKnJl53YgPzylalJKl91wUkakU8SUGdXtVLRLGdcumBxhpt/1QzoHA5KWfQbqtqe7lT4d1IHB/hL91oMJuo46twc7iCNdtsrgN4rJ7W2sATxgI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782773195; c=relaxed/simple; bh=lui/TN3E1W3uzarPwSNOLf+T0svkDeV8Nw/Plsdjcwk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=RtcyKX6xr3xh0px0AmYCSDjopzhWQ7FDbGeq0o5mIKKYSTIrHXsloJGw1b6gQmjzgPV/QuyqfhfH3a4bw0qsUzBcLBji7zLnbV5t0RLhN0kDcdhmzl9UnC2CBW6QrUKg4zmHeO1mznKOgRuwUiWpFppGmeF+Or0dNgEmabJvUlM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FBqEbyp1; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="FBqEbyp1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B335A1F000E9; Mon, 29 Jun 2026 22:46:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782773193; bh=LvtQOT1w607AXJpvAZlCEHoTQld1qa57ANws1Ah1o4Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=FBqEbyp1/Tnko9boOmLGRtzfous7Vq7W+sng5mOBVtL9TaWeZlznguqKG83b6e3yE bmW1Hwp78yaArZlt5Y2wn+iKt6HZJYKNWxv9QA0kicCqbHPjscQUrGBgOOgTj4JfFP vNVu4Ar1LG8D/Nv3szsMQt2IBUsmxPPdIylukXs6bcNh5WxwfU6FUK8fNBlZn8NHHi Bc0TDzbzXMtaq+WUWSF8LkE3TGeCeekAV0q8xA8RopbafHSMZAJzRcnQDHrro3M16B OVNEMuUL/eGdI4ph607NXIIL2FztQZvQwjAUfcPItMXgoz+aJjKFclrgZe6ixpNutR BH0c4uAo0uNlQ== Date: Mon, 29 Jun 2026 15:46:32 -0700 From: Drew Fustini To: sashiko-reviews@lists.linux.dev Cc: linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org Subject: Re: [PATCH v3 3/8] riscv: Add support for srmcfg CSR from Ssqosid extension Message-ID: References: <20260628-dfustini-atl-sc-cbqri-dt-v3-0-c9c1342fe3cf@kernel.org> <20260628-dfustini-atl-sc-cbqri-dt-v3-3-c9c1342fe3cf@kernel.org> <20260628212820.D0DD51F000E9@smtp.kernel.org> 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=us-ascii Content-Disposition: inline In-Reply-To: <20260628212820.D0DD51F000E9@smtp.kernel.org> On Sun, Jun 28, 2026 at 09:28:20PM +0000, sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: > - [Medium] Failing cpuhp_setup_state skips PM notifier registration, silently breaking QoS IDs across system suspend/resume. > -- > > commit e3ff463a672a85eb328bf3048323a464af88e408 > Author: Drew Fustini > > riscv: Add support for srmcfg CSR from Ssqosid extension > > This commit adds support for the srmcfg CSR defined in the Ssqosid ISA > extension. It introduces a per-task thread field and a per-CPU cache to track > Resource Control ID (RCID) and Monitoring Counter ID (MCID) fields, updating > the CSR during context switches. > > Link: https://github.com/riscv/riscv-ssqosid/releases/tag/v1.0 > > [ ... ] > > > diff --git a/arch/riscv/kernel/qos.c b/arch/riscv/kernel/qos.c > > new file mode 100644 > > index 0000000000000..c8900d91996f2 > > --- /dev/null > > +++ b/arch/riscv/kernel/qos.c > > [ ... ] > > > +static int __init riscv_srmcfg_init(void) > > +{ > > + int err; > > + > > + if (!riscv_has_extension_unlikely(RISCV_ISA_EXT_SSQOSID)) > > + return 0; > > + > > + /* > > + * cpuhp_setup_state() invokes the startup callback locally on every > > + * already-online CPU, so no separate seed loop is needed here. > > + */ > > + err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "riscv/srmcfg:online", > > + riscv_srmcfg_reset_cache, riscv_srmcfg_reset_cache); > > + if (err < 0) { > > + pr_warn("srmcfg cpuhp registration failed (%d), cpus brought online after boot will not invalidate the CSR_SRMCFG cache\n", > > + err); > > + return err; > > [Severity: Medium] > If cpuhp_setup_state() fails and returns early here, the > cpu_pm_register_notifier() registration is skipped, but the hardware > capability RISCV_ISA_EXT_SSQOSID remains active. > > Because returning an error from an arch_initcall does not halt the boot > process, the QoS feature will remain active in the kernel. > > If the PM notifier is not registered to invalidate the software cache upon > exit from low-power states, will subsequent context switches find a cache > match, mistakenly bypass the csr_write(), and execute tasks with the wrong > hardware QoS ID? Yes, it is possible. The early return in riscv_srmcfg_init() does skip cpu_pm_register_notifier(), and that notifier is what invalidates the per-cpu srmcfg cache across suspend/resume, so __switch_to_srmcfg() could find a stale match and skip the csr write. The risk is low, though. CPUHP_AP_ONLINE_DYN is a valid state, the registration name is not null, and riscv_srmcfg_reset_cache() cannot fail, so the only way cpuhp_setup_state() can fail is when no dynamic hotplug states remain. However, the fix is simple. The PM notifier is independent of the cpuhp state, so I'll change riscv_srmcfg_init() to register it even if the cpuhp setup failed. Thanks, Drew