From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35924) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cwV4x-0005TI-MO for qemu-devel@nongnu.org; Fri, 07 Apr 2017 10:41:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cwV4t-00072d-GJ for qemu-devel@nongnu.org; Fri, 07 Apr 2017 10:41:35 -0400 Received: from mail-wm0-x236.google.com ([2a00:1450:400c:c09::236]:33318) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1cwV4t-00072Y-9p for qemu-devel@nongnu.org; Fri, 07 Apr 2017 10:41:31 -0400 Received: by mail-wm0-x236.google.com with SMTP id y18so72729wmh.0 for ; Fri, 07 Apr 2017 07:41:31 -0700 (PDT) Date: Fri, 7 Apr 2017 15:41:28 +0100 From: Stefan Hajnoczi Message-ID: <20170407144128.GK16146@stefanha-x1.localdomain> References: <20170331084147.32716-1-haozhong.zhang@intel.com> <20170331084147.32716-5-haozhong.zhang@intel.com> <20170406101356.GC21261@stefanha-x1.localdomain> <20170406105309.4yqkqo3itlhkuy5o@hz-desktop> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="3MHXEHrrXKLGx71o" Content-Disposition: inline In-Reply-To: <20170406105309.4yqkqo3itlhkuy5o@hz-desktop> Subject: Re: [Qemu-devel] [RFC PATCH 4/4] nvdimm acpi: build flush hint address structure if required List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, Xiao Guangrong , "Michael S. Tsirkin" , Eduardo Habkost , Paolo Bonzini , Igor Mammedov , dan.j.williams@intel.com, Richard Henderson --3MHXEHrrXKLGx71o Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Apr 06, 2017 at 06:53:09PM +0800, Haozhong Zhang wrote: > On 04/06/17 11:13 +0100, Stefan Hajnoczi wrote: > > On Fri, Mar 31, 2017 at 04:41:47PM +0800, Haozhong Zhang wrote: > > >=20 > > > Add an boolean option 'flush-hint' to device 'nvdimm'. If it's on, a > > > flush hint address structure will be constructed for each nvdimm > > > device. > >=20 > > Users should not need to set the flush hint option. NVDIMM > > configurations that persist data properly without Flush Hint Addresses > > shouldn't use them (for best performance). Configurations that rely on > > flush hints *must* use them to guarantee data integrity. >=20 > It's for backwards compatibility, i.e. migrating a VM on QEMU w/o > flush hint support to another one w/ flush hint support. By using a > flush-hint option and making it disabled by default, users can ensure > both QEMU provide the same VM configuration. I think QEMU should play a role in deciding whether to use Address Flush Hints or not. We should not require the user to set a sensible value. If they get it wrong then they may suffer data loss! Stefan --3MHXEHrrXKLGx71o Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEcBAEBAgAGBQJY56UYAAoJEJykq7OBq3PIy74H/iG5NtXVqym24/Kq3uQ9I8Zd /OG6MglUw8K10j/nb+m56cAWQA2HUnkuB6gXCKLomWdnzll8roYU43fbrTs4zHb/ /vYSxpX1uAJAL74T5yLcYTBQaQ7hiXgki/D3ONBgM4pCddaKR4SUalF0Vp92u+cw zpzH/oYDd1Vb/9gcqk4WeylWaqtolYMitgliCh6muCJ9dzZR280XseJa3SBoki8Y fXmW4WxZLNtCijoH+K8ZnhNurhEnLsWSV5338fJcivkfvtVhIRw0lkNiunPx5GAF 7eFRWAlJrAVH+FHsZheFwSjkuGgbq3RvJxLqhoq0SpkCRvt6b6TeP09Sp8OCFAI= =WzBD -----END PGP SIGNATURE----- --3MHXEHrrXKLGx71o--