From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from ale.deltatee.com (ale.deltatee.com [204.191.154.188]) (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 D676D1F09B3 for ; Wed, 11 Jun 2025 19:42:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=204.191.154.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749670935; cv=none; b=ktyhiimyHCz9VwVBh8AAXQyjZ+6sqmoUsan4cCbvTDS/UBlNkxSVXYsT1vqLUc3TgnwHVr9ks4Ke6YzJNCpff+FUPW0iNtgb4ep/PpNvUyx5vIJ0oeYJTEEwSuVpFYxuZIc63LJau8ZEN7jTu4VJT9zPQILFbLJ15tkgry4YYWE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749670935; c=relaxed/simple; bh=wNwfZkthuRMPNbOZKFlk10p6MBTua0jJPrBJpjbCgCc=; h=Message-ID:Date:MIME-Version:To:Cc:References:From:In-Reply-To: Content-Type:Subject; b=FicXoZePtMhhP06XGAE5GmeUwtNCnhw1uboaiofGU8lW//CQuB9l4B63wF3+1fJw6ndoLIdbGHNzxzbrMLEujw3SprBfSSmcsn2L+KJR+G6cBF0aEE/Syq8ouRJtDDxuJ2Fl7GASwMbSai8KTM2qrZZC4QmupwN4PbiHMtr+PZg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=deltatee.com; spf=pass smtp.mailfrom=deltatee.com; dkim=pass (2048-bit key) header.d=deltatee.com header.i=@deltatee.com header.b=KPVQKLdD; arc=none smtp.client-ip=204.191.154.188 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=deltatee.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=deltatee.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=deltatee.com header.i=@deltatee.com header.b="KPVQKLdD" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=deltatee.com; s=20200525; h=Subject:In-Reply-To:From:References:Cc:To: MIME-Version:Date:Message-ID:content-disposition; bh=VSC4VLuuqrdFvSXDA+rlUN6veLmxqQV+QLrJEvwX08Q=; b=KPVQKLdDPsClMuuVGMBe8LXrmh G53AnrgF1N0xpZMb7vXcrT8nZVluJTX4rQ/LRLftfz5UKOqEdL0GBeeuDsTy7tgCFVRzFNyCRXKEO nJvfOePPPlZU55A4uKaElhDrKoGWcpUAE4Fci4V8SiT7YJRF/6BrsEbiQ9q52347jWGSmvw76nv2h MWc7nuD8tRw3MGjeXYz6bhcEqV2sufkKd3YyLExMkLwVSQu3QMWc1zxSouXITaPWKcCAIe8NvsNOG BV/QDRryc6YZ1FDJ4iYDhF/XFyyEc5ymlChDCt/ezgz/wm0P4Q9QN+4fOnQ78+RgxgHcYDAR/9tG7 vhbWMdIA==; Received: from d172-219-145-75.abhsia.telus.net ([172.219.145.75] helo=[192.168.11.155]) by ale.deltatee.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.96) (envelope-from ) id 1uPRKo-007k41-1S; Wed, 11 Jun 2025 13:42:05 -0600 Message-ID: <88fe6154-6086-409d-a180-665d62d72d47@deltatee.com> Date: Wed, 11 Jun 2025 13:41:54 -0600 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Keith Busch Cc: Christoph Hellwig , Jens Axboe , Sagi Grimberg , Chaitanya Kulkarni , Kanchan Joshi , Leon Romanovsky , Nitesh Shetty , linux-block@vger.kernel.org, linux-nvme@lists.infradead.org References: <20250610050713.2046316-1-hch@lst.de> <20250610050713.2046316-2-hch@lst.de> <20250611034316.GA2869@lst.de> <5cddbda3-02bd-4dc1-9f7f-197279da6279@deltatee.com> Content-Language: en-US From: Logan Gunthorpe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 172.219.145.75 X-SA-Exim-Rcpt-To: kbusch@kernel.org, hch@lst.de, axboe@kernel.dk, sagi@grimberg.me, kch@nvidia.com, joshi.k@samsung.com, leon@kernel.org, nj.shetty@samsung.com, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org X-SA-Exim-Mail-From: logang@deltatee.com X-Spam-Level: Subject: Re: [PATCH 1/9] block: don't merge different kinds of P2P transfers in a single bio X-SA-Exim-Version: 4.2.1 (built Wed, 06 Jul 2022 17:57:39 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) On 2025-06-11 10:41, Keith Busch wrote: > On Wed, Jun 11, 2025 at 10:39:17AM -0600, Logan Gunthorpe wrote: >> On 2025-06-11 10:26, Keith Busch wrote: >> That is all correct. In order to use P2P on a switch, with the IOMMU >> enabled, it is currently required to disable ACS for the devices in >> question. This is done with the command line parameter disable_acs_redir >> or config_acs. > > Is there some other mechansim that ensures a host memory mapped IOVA > doesn't collide with a PCI bus address then? Yes, in the absence of a switch with ACS protection this can be a problem. I haven't looked at this in a long time, but the iommu drivers reserve regions where the PCI addresses are valid so no iova will be allocated with a similar bus address. After a quick search, I believe today, this is handled by iova_reserve_pci_windows(). Logan