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 B37D048CD56 for ; Mon, 5 Oct 2026 13:30:08 +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=1791207011; cv=none; b=jrPuMy/Qg/HoA8DlavpORacvBC7nM6KJ/Av8sUXQdnxlROSAcQwIFptk5NLifXwnAw9wVC2m0scCTJraICS39TU/76rFrPKEtHTL15u9Ag1OB17DdfCfrWwP91hu4MiawpV/3caUMjLmMYYatGu93ftOia4AIM4/2MBG8H4ZLrI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791207011; c=relaxed/simple; bh=FTqKMAylXjfF2fqshVeCzYRnhDrYq84Jr96C5D2yQyQ=; h=From:Subject:To:Cc:In-Reply-To:References:Content-Type:Date: Message-Id; b=aNPPZ/mPyP5osH2oOGpEDZ/7+ISNWRL4+NJw2zkjZzEo4yZS9iDEtPYwqgS72VdxY1NTVZFac/2uzwffU4DGstl03yCkyfAC0Y9KpQO4l3Imi6AQNoSHCJyIz85XxqPH+Wbrn+5TzmcmGtXG2XTm5jMJb1moxShhUovZPPzI23Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gZybI73w; 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="gZybI73w" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A2EEE1F00893; Mon, 5 Oct 2026 13:30:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791207005; bh=zeSsoEe6T4xqqSAEswEgqsuIkBiBtbReZN3xc5IQV3c=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=gZybI73wjnS7mZnQ1lFzo8Rx/wgktU3MdkYgRL54Feu2jJBkHIyGyZLOoTiaizvSn UzGNOqjZet1OiBDeXZexQmRrmiES+kcb/Wr7dN16i+fBRMAiMMwfqTTkfhqJYbOoqo cjoS6deZfR6y5bLoEV7NrqwreyVo5+H6o8rJy9bAXx3osdyG4VGtGR9T3qo5wst8A8 P6gYh3rQDpsrFWxO4y1Hc5Ed1BdN33qaQacVpiZ1Z1DLPtNo9k6m5X5GrxZOCwdGiJ t3BNzoGBV8ip7imITYMcOfNBSzsX0Xmv1Blvq8UmXZMB/7h0Y2QNscBULUoBF3aVsF ydFPMD5jn+1Sw== From: sashiko-bot@kernel.org Subject: Re: [PATCH] PCI/P2PDMA: Add Intel Haswell client host bridge to the whitelist Reply-To: sashiko-reviews@lists.linux.dev To: "Scott Lee" Cc: linux-pci@vger.kernel.org In-Reply-To: <20261005132651.18368-1-dsix123@gmail.com> References: <20261005132651.18368-1-dsix123@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Mon, 05 Oct 2026 13:30:05 +0000 Message-Id: <20261005133005.A2EEE1F00893@smtp.kernel.org> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: > P2P DMA between two devices that do not share an upstream bridge is only > permitted when the traffic goes through a host bridge that is listed in > pci_p2pdma_whitelist[] with REQ_SAME_HOST_BRIDGE. >=20 > The Haswell client host bridge (8086:0c08, e.g. H97/H87/B85) is not in th= at > list, and cpu_supports_p2pdma() returns false on Intel, so > calc_map_type_and_dist() refuses P2P for any pair of devices behind > different root ports of the same host bridge, even though that root compl= ex > handles the traffic correctly. >=20 > Measured on an ASUS H97-PRO with a Xeon E3-1231 v3 (Haswell, 8086:0c08 at > 00:00.0) and two GPUs on separate root ports of that host bridge > (00:01.0 and 00:1c.4): >=20 > - pci_p2pdma_distance() < 0 before the change; peer access granted after > [ ... ] > pci_p2pdma_distance() all still apply. Tested on one board only, so the > usual caveat applies - broad testing on other Haswell boards would be > needed before this can be considered generally safe. >=20 > Signed-off-by: Scott Lee Sashiko has reviewed this patch and found no issues. It looks great! --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261005132651.1836= 8-1-dsix123@gmail.com?part=3D1