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 7A834348C7C; Mon, 12 Oct 2026 11:02:09 +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=1791802930; cv=none; b=RpEgxO8+f+Mhc9jRcHA0zM1vPLWEFQzfONlI9bGAiDJGp1jau9k8rg83AyFsoD/r1CaKNCr/LL210RCw3Sgs4MwtYBX3VXW/+Oq3XpVvYX5U2Gi+FgcO5CzlYnLe2ROs4INAtxGRt/Yj3NqB/LuZZNHLJJPiGy2JJK3FISFyEk4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791802930; c=relaxed/simple; bh=aj+gYybFQdwaLzcOujCEl6Ayb88eLjuLhCdZZHUlOxE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=AlEfr70YbN7dYy3XSTgFaTV+vCxOsMYZFigqOzhbzyG9TrgyMbAiqy0MNFaO1jOwvSpRGjnOSGg2oEfEU6Cp1sVwYtALHO+Y5Xs0s1kqOjIU4g8BaV/LdXAigQRK3NWfI1ATViyARkryRfXYs4eWYVM9JORkzIL6/M2FeR1Ufaw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BtvBiCKV; 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="BtvBiCKV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1728B1F0089B; Mon, 12 Oct 2026 11:02:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791802929; bh=MAfYAMjPNeKmn70tZ8yJzw3w1YF8t8B5YaHyVdbC17s=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=BtvBiCKVAPhg4YheaU0NRTp6NmOfBz71i/2zIRP+ixQZlDRLqv9KZ2Et0goaQhFpF 1adHNcrWs0a7uEmFieyjjaBhTuH/edNCuGf5KUXuHN+d31KNWCXCjrDUDy/uY8IDLj ao5nVaaGaM3ZuU2zQAZKdppFM3eRolLpwvA45qAEDycS2m7tXyRi46Kzr4N+vK83o0 krr9G8jYOmbF3ozKel1ofXEIzfyqphTOx0GaT0Id1f0N61X9eRhy9mKzsF/zW5S4mF sUDGOczGxsWpKhIstJfvyoiyO8ynN0redIjjsgQeIiEyNg9T4Pyqk0CnbhM/lWgwV3 vkCX5+ikp0/xg== Date: Mon, 12 Oct 2026 14:02:05 +0300 From: Leon Romanovsky To: Bjorn Helgaas Cc: Bjorn Helgaas , Logan Gunthorpe , Jason Gunthorpe , "Joerg Roedel (AMD)" , Will Deacon , Robin Murphy , Christian =?iso-8859-1?Q?K=F6nig?= , Thomas =?iso-8859-1?Q?Hellstr=F6m?= , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, iommu@lists.linux.dev, Tushar Dave , linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-rdma@vger.kernel.org, kvm@vger.kernel.org, Chaitanya Kulkarni , Greg Kroah-Hartman , Jens Axboe , Alex Williamson , Ankit Agrawal , Jonathan Corbet , Shuah Khan , Randy Dunlap , Sumit Semwal Subject: Re: [PATCH v9 01/18] PCI/P2PDMA: Document the TLP attribute assumptions Message-ID: <20261012110205.GD219304@unreal> References: <20261001-fix-p2p-acs-v4-0-v9-1-1a8e0f50ddd9@nvidia.com> <20261007201257.GA781492@bhelgaas> Precedence: bulk X-Mailing-List: linux-rdma@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: <20261007201257.GA781492@bhelgaas> On Wed, Oct 07, 2026 at 03:12:57PM -0500, Bjorn Helgaas wrote: > On Thu, Oct 01, 2026 at 02:55:09PM +0300, Leon Romanovsky wrote: > > From: Leon Romanovsky > > > > P2PDMA selects a mapping without receiving the Request's ordering or > > Address Type attributes. Its ACS handles only strictly ordered Requests > > carrying an Untranslated address. > > > > Document that the result is not defined for Relaxed Ordering or > > ATS-translated Requests because those TLP attributes can select different > > routes through the fabric. > > > > Reviewed-by: Logan Gunthorpe > > Tested-by: Tushar Dave > > Signed-off-by: Leon Romanovsky > > --- > > Documentation/driver-api/pci/p2pdma.rst | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > diff --git a/Documentation/driver-api/pci/p2pdma.rst b/Documentation/driver-api/pci/p2pdma.rst > > index 63cff9e4d2c9..80f8fec9b0e9 100644 > > --- a/Documentation/driver-api/pci/p2pdma.rst > > +++ b/Documentation/driver-api/pci/p2pdma.rst > > @@ -15,6 +15,13 @@ then based on the ACS settings the transaction can route entirely within > > the PCIe hierarchy and never reach the root port. The kernel will evaluate > > the PCIe topology and always permit P2P in these well-defined cases. > > > > +This evaluation assumes clients issue strictly ordered Requests carrying an > > +Untranslated address. Its result is not defined when clients use Relaxed > > +Ordering or issue ATS-translated Requests because those TLP attributes can > > +select different routes through the fabric. Unless ACS Translation Blocking > > +is enabled, a Port with ACS Direct Translated P2P enabled routes a > > +Translated Request directly to the peer regardless of the redirect controls. > > This whole paragraph is removed later in the series, so kudos for > documenting the current state before it changes :) This may be a leftover from the prerequisite fixes you merged. I'll keep it in the series for historical context. :) > > Unrelated to anything in this series, but this doc mentions > "p2p_provider", which doesn't exist. Should it be "p2pdma_provider"? Yes.