From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 C04A223D7F8 for ; Thu, 13 Nov 2025 15:56:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763049366; cv=none; b=siE/q4j2QZrmu3q3w7XFQjDOIR+emNd1nTbrfGnXK4ISK5h+10VNhm9nSHZCW/tGIVZnWmmByOqv6aGnydYVzOAdLYUNFNRFuOxp+A9mbUDDnjJuu5gwaSTFKLBL0Bu908guuawHdR5fJhaQSYtH/T8F2K3j8x2wKeca6Zzcpqs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763049366; c=relaxed/simple; bh=/YBERbDnlNvEEju8P6J9fLCKmEXJAW07il2rpCb+LQY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=fdy9kIT/WFyDd7V3Ch+c9Xa2rGx5Kvgt4bmGh56TkPpzqYOyg6Mzq6qaUo8BWPWek0oryAk8feYrVFh7/3YHtV8PfrY65jXf3qXabj4IP/BznGMSJbBBbxjkxIv4taaqdS5NE5Fxs4y79+2nqT2u80KWksklhRSNSzxDvejPSLE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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=hIkJ+u6G; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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="hIkJ+u6G" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1763049362; 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=miUKLDvjdcr115mhmReQ07Cxokwhp3zFzSa5up0L5NQ=; b=hIkJ+u6GharSjMFIq3dLiHAY720tZyRe0QvIYuB7IeSLSFEVsdeU0i8ka/zjhfYZLdJz3t gH6nai2SXL/FO1oJAeNYu/uXZ7sjggUnFBSPjEV518kFNTHyBU8OLSmxj0NGmKgVzwS2/U QoQ2EsCR8iOO6OhAFOXSX4/gbnvlR6g= Received: from mx-prod-mc-05.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-142-jnJ5IVUsMlOgbu9GMGxhJw-1; Thu, 13 Nov 2025 10:56:00 -0500 X-MC-Unique: jnJ5IVUsMlOgbu9GMGxhJw-1 X-Mimecast-MFC-AGG-ID: jnJ5IVUsMlOgbu9GMGxhJw_1763049359 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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 8DBA11956080; Thu, 13 Nov 2025 15:55:59 +0000 (UTC) Received: from localhost (unknown [10.2.16.177]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id A6CE2300018D; Thu, 13 Nov 2025 15:55:58 +0000 (UTC) Date: Thu, 13 Nov 2025 10:55:57 -0500 From: Stefan Hajnoczi To: Alberto Faria Cc: virtio-comment@lists.linux.dev, mst@redhat.com, dverkamp@chromium.org Subject: Re: [PATCH v4] virtio-blk: Add support for "Force Unit Access" writes Message-ID: <20251113155557.GD189474@fedora> References: <20251112055113.62207-1-afaria@redhat.com> Precedence: bulk X-Mailing-List: virtio-comment@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="//My83XEFAD5o8g2" Content-Disposition: inline In-Reply-To: <20251112055113.62207-1-afaria@redhat.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 --//My83XEFAD5o8g2 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Nov 12, 2025 at 05:51:13AM +0000, Alberto Faria wrote: > Add a VIRTIO_BLK_F_REQ_FLAGS feature bit converting the current > `virtio_blk_req::reserved` field into a `flags` bit field, which can be > used to modify the behavior of an entire request. The meaning of each > bit depends on the request type. >=20 > Define a single VIRTIO_BLK_REQ_FLAG_OUT_FUA bit as signaling that a > VIRTIO_BLK_T_OUT request should be a "Force Unit Access" (FUA) write, > i.e., should become stable once the request completes. FUA writes enable > better performance compared to the alternative of waiting for a write to > complete and subsequently submitting a flush. >=20 > Also add a VIRTIO_BLK_F_REQ_FLAGS_OUT_FUA feature bit indicating device > support for the aforementioned FUA bit. >=20 > This approach allows for future expansion to other request-level flags > and allows the same flag bit to be used for different purposes on > different request types. The VIRTIO_BLK_F_REQ_FLAGS feature bit ensures > compatibility with legacy devices/drivers that interpret the > previously-`reserved` field as a priority indicator. >=20 > Signed-off-by: Alberto Faria > --- >=20 > v4: > - Have the semantics of each request flag depend on the request type, as > suggested by Stefan. > - Some other smaller rewordings suggested by Stefan. >=20 > v3: > - Changed to a more future-proof approach somewhat similar to what was > suggested by Stefan. > - Included a brief rationale for the introduction of FUA write requests, > as suggested by Michael. >=20 > v2: > - Redefine VIRTIO_BLK_T_OUT_FUA to 27 since 15 is already in use. > - Clarify that the cache mode has no impact on VIRTIO_BLK_T_OUT_FUA > semantics. > - Allow drivers to negotiate VIRTIO_BLK_F_OUT_FUA even if they are > incapable of sending VIRTIO_BLK_T_OUT_FUA commands. >=20 > device-types/blk/description.tex | 43 +++++++++++++++++++++++++++++--- > 1 file changed, 39 insertions(+), 4 deletions(-) Reviewed-by: Stefan Hajnoczi Please see here on how to bring this issue to a vote: https://github.com/oasis-tcs/virtio-spec/tree/master?tab=3Dreadme-ov-file#u= se-of-github-issues Thanks, Stefan --//My83XEFAD5o8g2 Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmkV/40ACgkQnKSrs4Gr c8gayggAnUjM5GEcHbUWb6GYAylqRbBXB3RhwBnafsqv7/mvMrBP1sN87rIHZqCB t/GwE+yT+7t44A3huGLXNJNjueKxdIeF4zw6FA9xmyxWzZomLbdswZtImy+MeTBC V8DYbagb9wSG5VKXWC1IOoxvcD290hvdtKlH9n1C21XsGKAmY59yCiFLenjuBmJE cmPvS0MjTKfbMvwVcYO83yZ3yS8snKC/uu7eKl1emVlnJ7gozO3cDjlRg3Q7R/I8 LGF5Vb3mRqU9ZZIqJYD0QrI/sqvbSRb+zM/hn/KAyycKVLrhuYbXTsi5AM85FDNZ XX2rOc3JPmGmxRPrOzPJldkVGjuF3Q== =Qykw -----END PGP SIGNATURE----- --//My83XEFAD5o8g2--