From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 6B8561ADC85 for ; Thu, 23 Jan 2025 20:00:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737662416; cv=none; b=pUEGjymrZhtm0GrKZ4VMRgsC5sYvRa48aIPzv/V3fetFIiA5/ZGpIoBXCJFC9W99dRtBMmGPjSU9M4ZDY3pX3VyAjMEXNBSBB1iTqM7EPLewPJCz8B4Q3Bj8+iMR5hnPwead2n/iAbDG0PiZ2PSxUuD33B4OMTAMwreQRAI7Agc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737662416; c=relaxed/simple; bh=ccchkg54xM3AXV7CPGq2n8b881J16v+c23V9c8T46xk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=VyNzisxawtUhvnupdcvC2wXmxu7mBPNkCzWVTf23B2rg/t6chOBErsjn9Tq3n0SHyTJkBuNZR8yhgRftFrAl8jtfG6x8N3MAtt16xff0p6wKftB87aJJMQkfptbTyNl17+PcCwb3VU3EWRfKWL0XJu2uujqqlEdlajue4Dj022E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Bd/mPboq; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Bd/mPboq" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1737662413; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ccchkg54xM3AXV7CPGq2n8b881J16v+c23V9c8T46xk=; b=Bd/mPboqzq917oG/ZiQ74CbKEnfHua/flcpphsWTub+nGLTzzGsa7GFGP5YGdRYwcFyU0a jQwuBcsA8DngYEai1fh7hYypRFpR4OxYsoMboriRIbPQ4phuBzG92mC15purtp1PLPNflz xu1pKSHbXsS3Pb7cZwlai22AXEVTpCI= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-57-r3vJYF2kOt2oRZDC08iwcw-1; Thu, 23 Jan 2025 15:00:09 -0500 X-MC-Unique: r3vJYF2kOt2oRZDC08iwcw-1 X-Mimecast-MFC-AGG-ID: r3vJYF2kOt2oRZDC08iwcw Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 800821955DCB; Thu, 23 Jan 2025 20:00:08 +0000 (UTC) Received: from localhost (unknown [10.2.17.59]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 274853003E7F; Thu, 23 Jan 2025 20:00:06 +0000 (UTC) Date: Thu, 23 Jan 2025 15:00:06 -0500 From: Stefan Hajnoczi To: Eugenio Perez Martin Cc: Jason Wang , mst@redhat.com, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, Hanna Reitz , Xuan Zhuo , German Maglione Subject: Re: [PATCH] vduse: add virtio_fs to allowed dev id Message-ID: <20250123200006.GB238888@fedora> References: <20250121103346.1030165-1-eperezma@redhat.com> <20250122154908.GB178738@fedora> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="eIh4olyubDqwvDA0" Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 --eIh4olyubDqwvDA0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Jan 23, 2025 at 08:26:57AM +0100, Eugenio Perez Martin wrote: > On Thu, Jan 23, 2025 at 2:50=E2=80=AFAM Jason Wang = wrote: > > > > On Wed, Jan 22, 2025 at 11:49=E2=80=AFPM Stefan Hajnoczi wrote: > > > > > > On Tue, Jan 21, 2025 at 11:33:46AM +0100, Eugenio P=C3=A9rez wrote: > > > > A VDUSE device that implements virtiofs device works fine just by > > > > adding the device id to the whitelist. > > > > > > The virtiofs DAX Window feature might require extra work. It is not > > > widely enabled though, so must virtiofs devices will work fine with j= ust > > > virtqueue and configuration space support. > > > > +1. > > > > The DAX Window may help to reduce the bounce buffer copying and fit > > for the case where an AI application just accesses one single large > > file. > > > > We need to consider implementing this via VDUSE. > > > > Thanks > > > > >=20 > I thought DAX can only be applied in the VM case. Is it possible to > apply it using virtio_vdpa? Hardware could implement the DAX Window feature. In virtio-pci it's implemented as a range within a BAR on the PCI device. > Is it possible to detect that the device is trying to use DAX so it > fails the negotiation? Yes, DAX is optional. It's only available when the device reports a Shared Memory Region with ID 0: https://github.com/oasis-tcs/virtio-spec/blob/master/device-types/fs/descri= ption.tex#L233 Just to let you know, the QEMU vhost-user implementation of the DAX Window is not complete. In the past David Gilbert had out-of-tree patches to enable it in QEMU. The guest driver support is in Linux. Stefan --eIh4olyubDqwvDA0 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmeSn8UACgkQnKSrs4Gr c8ihVAf+JTUE11Fdx20jO2oLb9js62qQg2RyGp4HLBFVTrTNfIThk9oxBLYmqJUd FfcPXKaOei/ildxs/afpNFPPLYYDLxSmcs2EqyxU9UArVcN7DnEb+EqjUvph9NA9 qPhhZh/vULjFQB+3hTUSFSdIlOsKqFuvmdGfH4/vUxMs9eGYbrr0iDcr3tauRV7Y nyPoRz1HprUQLVb5gQ78JBunjqVcOQ5mhiKERxwBGDRCmYEbZ3KVqWvHVUNEwyR0 rlFaFClKUZuPhU7MbIYGbnTevzDUx2X9R+6avN3kYVOnhLUU9+1ZDqQrx9M2noIg hF2LOX7mM4oHR1sNfebn5ehArAIvHA== =3Yyv -----END PGP SIGNATURE----- --eIh4olyubDqwvDA0--