From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793733830; b=23wjbtjdjo5PfIG2wtSI6r5KlfsuUq5Wob19O/QzHdBzJD4fanCl2MF5BqF2NH6YBH5/ XA6wBoihCASrRTuJrx0v2itfrUmzehCI7HiXTI7BtAlEge6cQAZOuXlHiYe8ILEprx2rW Hm+mAEoglJxWTsyF8fMpxPopAhJVCS2vzY6NvBZ14gGRnkQu39d4up5Ku3+bFD/7QvXl/ ndsRlMJ0mf6tAKkYWr2G06eMVJgpL3SVbIyxMDirhn6p2l1VJuV6s7gKqPLTlSPqhi/F6 UGoncdslQyVlI3Zz8RfuC3ovkT22t2ssFPHhAi9I6a+2mNsjR+9oCqGRZPvSy8U5lDQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793733830; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=bM/PWZRdJ5vBkRuduM2rCijVDP1L8R0XfcxtbD8OeCI=; b=Tv7HUuCG7NVsBn2H1YHzbfr07TArhlfZXm8Rsukl9t4mkSyiENTZdDwnR+YwFjH2gtvk 6RjjPtIuwt3hPQ5CSmlITNeu7K/HsFSjMCfLbQeQfIYSWuFyDqzfI2jHNCjuDWPtmj5iN A+AigmkO2nCEcTIgea2bTOadDvwC0mMj5iG+A/OpY52HrY3cqUBZUzkUGbMccecPxGgAR +mfbQXhhLcUpngUxf5iTYtMU/HWi7awYqx/+Un+akJeMqRVsktf2ylZO+LAy0bGazL+gX 03bq1q9mKpGstILEv8iIOsHg4FL5e/vOT7DNpUH30uQ260MJUOFibJu9zmLmlrFSAIg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Sz+30YTR; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 80BA1606A31B for ; Tue, 3 Nov 2026 19:23:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Sz+30YTR Received: by smtp.kernel.org (Postfix) with ESMTPSA id 16E271F00A18; Tue, 3 Nov 2026 19:23:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793733830; bh=bM/PWZRdJ5vBkRuduM2rCijVDP1L8R0XfcxtbD8OeCI=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=Sz+30YTRD2/EsA5GkBkTT8AxO9EUIZeHGagBxfM6UBxTfNMDfgvvH61DybWS2BQGB UllWXK7LbLzbvr7p/MSSsaXvCPt2XbTW8fxa0SDlerHfyxi3NpmeCTAq9BeWYIiRfz hcJiVxBwTbY+DDv+k0id3FwkR/AIOOqvkKRZOxzzu9EbTuWUBBqUk69HxMfQ/4u6ly HdxGdRu+Av5US0kW1TBa/5eYzt0vH6LpgSP0jf28rJIsNTiTZc7fV/hW0h/VMlqNGY CuYJa54b1/eA7H7LiAgZ/Qu879S3P+OJE3uqxiodj9WhW6nVb0ltDYurXDcl+/+Geh pwmzquWC6ENFg== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH for 7.5] pci: Support preferring MMCONFIG for all config space accesses Reply-To: sashiko-reviews@lists.linux.dev To: "Josh Triplett" Cc: linux-pci@vger.kernel.org In-Reply-To: References: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Tue, 03 Nov 2026 19:23:49 +0000 X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list > Even when MMCONFIG is available, PCIe currently defaults to IO-based > accesses for the first 256 bytes of config space. >=20 > IO-based accesses are serialized, and can cause substantial scalability > issues when initializing a large number of devices on a system with many > CPUs. (Those often coincide, because many systems have PCIe devices per > CPU.) >=20 > Add a `pci=3Dprefer_mmconf` option to use MMCONFIG for all config space > accesses. Also add a Kconfig option (default n) to make that the > default, allowing a boot-time opt out with `pci=3Dno_prefer_mmconf`. >=20 > Tested on an AWS c8i.48xlarge system, with 192 CPUs, over five boots > with and five boots without. >=20 > Without: > PCI init 266ms > Boot to minimal /init 726ms >=20 > With: > PCI init 213ms (~20% faster) > Boot to minimal /init 661ms (~9% faster) >=20 > Signed-off-by: Josh Triplett Sashiko has reviewed this patch and found no issues. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/e1b3a7d153da74d3c50= d7c90696b2881f4c0e97d.1793727991.git.josh@joshtriplett.org?part=3D1