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=1793089225; b=IzOhQDvZheOpesbf9RE4aO0ukG82lh0EvvfFwpOSi9bIQ1pl6QEocixEHuIJ1q1Fl/7Y 7a2IsW8aco/s23NzO7XOZqvoQUZpzy1DjkYMqVKfBUYQmcZN868I5HyOj+0ak63Ue85bx s13tNF/2OQ2/hWx5DFO9cjeB/HrVpasi/FkpOneO+Pq5oAwnTNzi8J9HY7poupPdv2UH5 Dt1ULMReKSPblJS3cG71O/h/4kfNhW6nUH+aIH72X8eyUFqBe+n2Cvp7K+iXVEtp95BA6 uAta78pz+FF+hEJE3EUwYbgaGaKvscAICiS5dEobygqEMEaTTfPFcbo5r049Qav3CmA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793089225; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=Dc6nTbgetndJa/rEduwSnVZsvBL0h+BNt60D8sM05u4=; b=PqZqZDY7RfPMUVrbG4P97N879DXjTUcxGVF+VsZSPDgSeZK0+8mNKkC5uReXNoU13+KU ZkkybKrx8/O9HFbIYvfKE+xQuKr/Ehed3A/BPWQwv4Qk//Qs8qRuXW1lBGZPqLInhYL+3 6rAaRbTauOM138vv3NSY+fTRn79hhTG2RDqNZkGYpjw3gSaJtVa2WK7Wo2QUUW8n+Gsos PJnnFEq/kYaibmelpi2aD06k+vUWrziyE4qmGUzrHm3MNG6DOWb5Hm3EkgcTEWJgm4eS1 NKK3JvFRXhS7aL68FVZlUz5J57P80rnUSMUQD34MELSQPz/52mWb6A6MZeVxj26fSJQ== 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=X66XoZki; 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 8C079606A31A for ; Tue, 27 Oct 2026 08:20:25 +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=X66XoZki Received: by smtp.kernel.org (Postfix) with ESMTPSA id EE1301F01825; Tue, 27 Oct 2026 08:20:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793089225; bh=Dc6nTbgetndJa/rEduwSnVZsvBL0h+BNt60D8sM05u4=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=X66XoZkiui+uOtFx6VYcmJJq/xNmu5dvh2ryXC4E3g2C6CWkWKyU3ZpzI6O7/7hAK LliASgVHCh9LW74M3dpoeljgFV5HwO4i8ODDNZHPkW/7WS9f8hL3GQp0aD1dZtqyBU 5NvDtb0sz2O8kGMAEmGAqXZd/EO32sE5cPt/1phDyxaZ4a6vGNrOWn4eGnwWedSa11 yzquAXH4ZC85PfFttssd34m3c4vlcjK+4y4nG4lMwkVjjr636BBzWTM0zHYgwWhg7s 7F1HPUe1aso2NqcemFNw4vkR/4R7pX63x8TfF3V/NGDhgLIVGR2wTPrBdTdXgrvGiU Q65tUUIAUM6yA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH] 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, 27 Oct 2026 08:20:24 +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/a7d2b402784a409f556= 4c1fdce77a41e09f29280.1793087687.git.josh@joshtriplett.org?part=3D1