From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 5630123BD0E; Wed, 2 Apr 2025 15:12:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743606771; cv=none; b=J8SHpfNDp0SelI6vqJeRez/ukTFmiZWnGIiNIcYXqGHG+vOzfGiw+jehw/fjuVj1bFINguuzexMcyX1NeqHTb9DZpTG65WNMKjq/cm+q3+bkZKgjyF/x9G37SRYHlw0XiORoRBF3YQrocGJN6eL7R/Vja9PMcMbHKoUTpmGWDvw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743606771; c=relaxed/simple; bh=dUygldecw0c67KznZYR7Vjqsp8sEub6i1SevQhTsidw=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=Qye47W/fvyLnnL5nYpyO9J8/uNxVbAAw6h7IeyxYVzjzD5yD52XFTRz4NexcC3MFT9VCD7Oha0R06uG3q9ueyZvixmFOP6Xv7fdK5mI1+tYc0T5USqIEXFHlFr80cYTzC5vHZ5Rk/f5XhYZZqz3MgUBsbN3C5MN+i/jU/fXt+og= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=desiato.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=KwOr7lEn; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=desiato.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="KwOr7lEn" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=MIME-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=dUygldecw0c67KznZYR7Vjqsp8sEub6i1SevQhTsidw=; b=KwOr7lEndrR7cQORTS4hQOsXIN PZI5TurgxaeOQe+dJQNW7/pc1CFjLELf40i0cOKvvDmFloehY4ATHSuw++2aGoyl8LvoD8RH1QTNE xTp5Rc5erhaSQIa+2EAmHy9gMV/cshtLOEzZ68iHfZa72ESZ4c0N/vI3admfdhZl38C057n2DyrRc 6jaiuDQDYQDIpw2kcANRFVjDMR4Dje9/ot04jHF2FT/2P218tnWYabKVKyO388Nci8HFgOhKgT8FW KdJM4Ww8QzzIzVhFPpwX7M3U6KJFChunRM6VFh/vAqzhnUHVY4ZabSGguFTt8R0HWre8xMD2P8s8T iJ4N/+xA==; Received: from [172.31.31.145] (helo=u09cd745991455d.ant.amazon.com) by desiato.infradead.org with esmtpsa (Exim 4.98.1 #2 (Red Hat Linux)) id 1tzzlf-000000073fQ-2gat; Wed, 02 Apr 2025 15:12:39 +0000 Message-ID: <19ba662feeb93157bc8a03fb0b11cb5f2eca5e40.camel@infradead.org> Subject: Re: [RFC PATCH 1/3] content: Add VIRTIO_F_SWIOTLB to negotiate use of SWIOTLB bounce buffers From: David Woodhouse To: "Michael S. Tsirkin" Cc: virtio-comment@lists.linux.dev, hch@infradead.org, Claire Chang , linux-devicetree , Rob Herring , =?ISO-8859-1?Q?J=F6rg?= Roedel , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, graf@amazon.de Date: Wed, 02 Apr 2025 16:12:39 +0100 In-Reply-To: <20250402105137-mutt-send-email-mst@kernel.org> References: <20250402112410.2086892-1-dwmw2@infradead.org> <20250402112410.2086892-2-dwmw2@infradead.org> <20250402105137-mutt-send-email-mst@kernel.org> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-uz/vACq+b3ETFGJm9ikf" User-Agent: Evolution 3.52.3-0ubuntu1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html --=-uz/vACq+b3ETFGJm9ikf Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, 2025-04-02 at 10:54 -0400, Michael S. Tsirkin wrote: > > +=C2=A0 If a the device transport provides a software IOTLB bounce buff= er, > > +=C2=A0 addresses within its range are not subject to the requirements = of > > +=C2=A0 VIRTIO_F_ACCESS_PLATFORM as they are considered to be ``on-devi= ce''. >=20 > I don't get this part. the system designers currently have a choice > whether to have these controlled by VIRTIO_F_ACCESS_PLATFORM or not. > with PCI, for example, BAR on the same device is naturally not > behind an iommu. In the PCI case this *is* a BAR on the same device, and is naturally not behind an IOMMU as you say. This is just stating the obvious, for clarity. For virtio-mmio it also isn't translated by an IOMMU; that was the *point* of the `restricted-dma-pool` support. --=-uz/vACq+b3ETFGJm9ikf Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCD9Aw ggSOMIIDdqADAgECAhAOmiw0ECVD4cWj5DqVrT9PMA0GCSqGSIb3DQEBCwUAMGUxCzAJBgNVBAYT AlVTMRUwEwYDVQQKEwxEaWdpQ2VydCBJbmMxGTAXBgNVBAsTEHd3dy5kaWdpY2VydC5jb20xJDAi BgNVBAMTG0RpZ2lDZXJ0IEFzc3VyZWQgSUQgUm9vdCBDQTAeFw0yNDAxMzAwMDAwMDBaFw0zMTEx MDkyMzU5NTlaMEExCzAJBgNVBAYTAkFVMRAwDgYDVQQKEwdWZXJva2V5MSAwHgYDVQQDExdWZXJv a2V5IFNlY3VyZSBFbWFpbCBHMjCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAMjvgLKj jfhCFqxYyRiW8g3cNFAvltDbK5AzcOaR7yVzVGadr4YcCVxjKrEJOgi7WEOH8rUgCNB5cTD8N/Et GfZI+LGqSv0YtNa54T9D1AWJy08ZKkWvfGGIXN9UFAPMJ6OLLH/UUEgFa+7KlrEvMUupDFGnnR06 aDJAwtycb8yXtILj+TvfhLFhafxroXrflspavejQkEiHjNjtHnwbZ+o43g0/yxjwnarGI3kgcak7 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