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 17492331ED3; Thu, 13 Aug 2026 16:55:52 +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=1786640153; cv=none; b=PCStXZeBNmOG25Yv8TTEtAZu1cXHQ33BDAIbf//osBnFUh/amA+Mruf6SQSRmJTQKgJPL7uVj3Ol5HXV9d9t2oTRzbwCW9imP6/fpug6fQaGFTgHcI9qwC1tDM6gAKYvEaxaYPjOTd2qHWNBP7yIb5gW0dp6QlN2KmHbYqo+YMA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786640153; c=relaxed/simple; bh=Zv5o0SHQTncQAW6YUYvW2MVxlBiqHwG0omIZb6cl/Uo=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=f8gKbPFt/pNcEc/llnKXQqxwHxRGjX32vb1EOmWWLcSNK9z5NEB+F27YGfVvRqDHPLFu6Q1aHFsEE42gXxugtu6TZMpGz7UuPksthy/KNZQiquyFCFcJ3FnnOGkH7S1wKaROWncVjZpyB4Cf6vOoGCzNumtNA2Lv49hrhz6Xbd0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=G59OR5O1; 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="G59OR5O1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BF7771F000E9; Thu, 13 Aug 2026 16:55:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786640152; bh=j1RttWiTjaY52255xEPE0Lhej03QMUfsKVp50o+E/Fk=; h=Date:From:To:Cc:Subject:In-Reply-To; b=G59OR5O1w6mvCga2Aly1seWK/YBF1/KPdgm2xdH7gPAyPXtCZDvXva/IqipsBAeyE 1OfBt6f3YBsVeIxfJE/1fwgUmnR+XZcvGojZCaskLhZT4FM6LZnISfvBdZMwNiAah+ Mms7EbI7gp5VaF2zjmMW6zheoDeYbgTk2HN/+2enbLe5C3o6srHm+ddbLapvXt4Wp+ wxW10trBJkt+GIowrvHewu142n75UZDiqXXQwbJZmrQ8BaLmNKae6OH5dIoRQt3dIn a3jZeTIhUIhwdiFj6oxo21JgHVEI+S7aTR8VjKQKMavy1mqiKNdq0EbOSJQrY6VBcG KgITYAQ8Z7iRA== Date: Thu, 13 Aug 2026 11:55:50 -0500 From: Bjorn Helgaas To: Mohamad Raizudeen Cc: bhelgaas@google.com, alex@shazbot.org, skhan@linuxfoundation.org, jkoolstra@xs4all.nl, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] PCI: Fix 32-bit config write in Intel RP MPC ACS quirk Message-ID: <20260813165550.GA1140467@bhelgaas> 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: <20260723171203.4892-1-raizudeen.kerneldev@gmail.com> On Thu, Jul 23, 2026 at 10:42:03PM +0530, Mohamad Raizudeen wrote: > The pci_quirk_enable_intel_rp_mpc_acs() reads a 32 bit DWORD from the > MPC register, sets bit 26 (INTEL_MPC_REG_IRBNCE), but it writes it back > using pci_write_config_word(). > > Because bit 26 resides in the upper 16 bits of the 32 bit register, a 16 > bit write to offset 0xd8 completely drops the newly set bit. The quirk > logs that it is enabling IRBNCE, but the hardware never actually > receives the command. > > Fix this by using pci_write_config_dword() to ensure the full 32 bit > value is written back to the hardware. > > Fixes: d99321b63b1f ("PCI: Enable quirks for PCIe ACS on Intel PCH root ports") > Signed-off-by: Mohamad Raizudeen Applied with stable tag to pci/virtualization for v7.3, thank you! > --- > Changes in v2: > - Added "Fixes:" tag and CC'd Alex Williamson as requested by Bjorn Helgaas. > > Link to v1: https://lore.kernel.org/linux-pci/20260723160641.GC836122@bhelgaas/T/#t > > drivers/pci/quirks.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c > index b09f27f7846f..0d0cf6f86173 100644 > --- a/drivers/pci/quirks.c > +++ b/drivers/pci/quirks.c > @@ -5361,7 +5361,7 @@ static void pci_quirk_enable_intel_rp_mpc_acs(struct pci_dev *dev) > if (!(mpc & INTEL_MPC_REG_IRBNCE)) { > pci_info(dev, "Enabling MPC IRBNCE\n"); > mpc |= INTEL_MPC_REG_IRBNCE; > - pci_write_config_word(dev, INTEL_MPC_REG, mpc); > + pci_write_config_dword(dev, INTEL_MPC_REG, mpc); > } > } > > -- > 2.53.0 >