From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38698) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cb7ni-0000eR-QT for qemu-devel@nongnu.org; Tue, 07 Feb 2017 10:35:28 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cb7nf-0003KL-Kq for qemu-devel@nongnu.org; Tue, 07 Feb 2017 10:35:26 -0500 Received: from mx1.redhat.com ([209.132.183.28]:41724) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cb7nf-0003Js-FP for qemu-devel@nongnu.org; Tue, 07 Feb 2017 10:35:23 -0500 Date: Tue, 7 Feb 2017 17:35:19 +0200 From: "Michael S. Tsirkin" Message-ID: <20170207173429-mutt-send-email-mst@kernel.org> References: <28ff6ff023dd041fc7557955dea916adce72efea.1486285434.git.ben@skyportsystems.com> <20170206170455-mutt-send-email-mst@kernel.org> <20170206193300-mutt-send-email-mst@kernel.org> <20170207150032.2807d29f@nial.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20170207150032.2807d29f@nial.brq.redhat.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v5 05/10] ACPI: Add Virtual Machine Generation ID support List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Igor Mammedov Cc: Ben Warren , qemu-devel@nongnu.org, lersek@redhat.com On Tue, Feb 07, 2017 at 03:00:32PM +0100, Igor Mammedov wrote: > On Mon, 6 Feb 2017 19:41:36 +0200 > "Michael S. Tsirkin" wrote: >=20 > > On Mon, Feb 06, 2017 at 09:29:30AM -0800, Ben Warren wrote: > > >=20 > > > On Feb 6, 2017, at 8:15 AM, Michael S. Tsirkin = wrote: > > >=20 > > > On Sun, Feb 05, 2017 at 01:12:00AM -0800, ben@skyportsystems.co= m wrote: > > >=20 > > > From: Ben Warren > > >=20 > > > This implements the VM Generation ID feature by passing a 1= 28-bit > > > GUID to the guest via a fw_cfg blob. > > > Any time the GUID changes, an ACPI notify event is sent to = the guest > > >=20 > > > The user interface is a simple device with one parameter: > > > - guid (string, must be "auto" or in UUID format > > > xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx) > > >=20 > > > Signed-off-by: Ben Warren > > >=20 > [...] >=20 > > >=20 > > > This variable name was suggested by Laszlo. the =E2=80=98a=E2=80=99= in =E2=80=98vgia=E2=80=99 refers to > > > address, but I=E2=80=99ll add some comments. =20 > >=20 > > vmgenid_addr_le? > >=20 > >=20 > > > How about we make it 8 byte so it's future proof? > > >=20 > > > I can do that, but a previous conversation we had made it clear tha= t guests > > > would never allocate above 4GB so 64 bits wasn=E2=80=99t necessary.= =20 > >=20 > > Right, it's just very painful to change once we make it 32 bit. > I'd keep it 32 bit since it's in variable in global AML context and our > table revision is 1, so per spec OSPM should handle it as 32 number. > Chances of guest survival on boot would depend on AML interpreter toler= ance > to AML errors, which for windows usually is 0 and leads to non obvious = BSOD. > If we leave DWORD, even XP will be able to boot fine and only report > unknown device. AML reports 2 DWORDS per spec, no issue there. I guess it's exactly for XP compatibility.