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[79.178.2.19]) by smtp.gmail.com with ESMTPSA id d22sm5514698qte.93.2020.03.10.23.29.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Mar 2020 23:29:21 -0700 (PDT) Date: Wed, 11 Mar 2020 02:29:16 -0400 From: "Michael S. Tsirkin" To: Liran Alon Subject: Re: [PATCH v2 00/16]: hw/i386/vmport: Bug fixes and improvements Message-ID: <20200311022120-mutt-send-email-mst@kernel.org> References: <20200310165332.140774-1-liran.alon@oracle.com> <20200310133932-mutt-send-email-mst@kernel.org> <20200310164239-mutt-send-email-mst@kernel.org> <20200310173020-mutt-send-email-mst@kernel.org> <95fdfa38-1ef1-8735-2d50-e24c8a909144@oracle.com> <20200310175825-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: nikita.leshchenko@oracle.com, ehabkost@redhat.com, qemu-devel@nongnu.org, rth@twiddle.net Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Mar 11, 2020 at 12:19:59AM +0200, Liran Alon wrote: >=20 > On 11/03/2020 0:00, Michael S. Tsirkin wrote: > > On Tue, Mar 10, 2020 at 11:57:49PM +0200, Liran Alon wrote: > > > On 10/03/2020 23:44, Michael S. Tsirkin wrote: > > > > On Tue, Mar 10, 2020 at 02:29:42PM -0700, Liran Alon wrote: > > > > > On 10/03/2020 22:56, Michael S. Tsirkin wrote: > > > > > > On Tue, Mar 10, 2020 at 08:09:09PM +0200, Liran Alon wrote: > > > > > > > On 10/03/2020 19:44, Michael S. Tsirkin wrote: > > > > > > > > On Tue, Mar 10, 2020 at 06:53:16PM +0200, Liran Alon wrote: > > > > > > > > > Hi, > > > > > > > > >=20 > > > > > > > > > This series aims to fix several bugs in VMPort and improv= e it by supporting > > > > > > > > > more VMPort commands and make command results more config= urable to > > > > > > > > > user via QEMU command-line. > > > > > > > > >=20 > > > > > > > > > This functionality was proven to be useful to run various= VMware VMs > > > > > > > > > when attempting to run them as-is on top of QEMU/KVM. > > > > > > > > >=20 > > > > > > > > > For more details, see commit messages. > > > > > > > > Well two versions in one day and some review comments weren= 't addressed. > > > > > > > There is a single review comment that wasn't addressed which = is replacing an > > > > > > > enum with a comment. And I explicitly mentioned that it's bec= ause I want > > > > > > > additional opinion on this. > > > > > > > I don't see why such a small thing should block review for 15= patches... > > > > > > > All the rest of the comments (Which were great) have been add= ressed. Unless > > > > > > > I have mistakenly missed something, which please point it out= if I did. > > > > > > OK I just took a quick peek, two things quickly jumped out at m= e. > > > > > Thanks for having a look. > > > > > > version property really should be a boolean and have some docum= entation > > > > > > saying what functionality enables. > > > > > I thought that having a version number approach is more generic a= nd easy to > > > > > maintain going forward. > > > > > If I understand correctly, this is also the approach taken by qxl= & qxl-vga. > > > > >=20 > > > > > The more elaborate alternative could have been introducing compat= _flags (As > > > > > PVSCSI does) but it seems like it will pollute the property space= with a lot > > > > > of useless VMPort properties. > > > > > (E.g. x-read-eax-bug, x-no-report-unsupported-cmd, x-no-report-vm= x-type and > > > > > etc.). > > > > >=20 > > > > > What is the advantage of having a boolean such as "x-vmport-v2" i= nstead of > > > > > having a single "version" property? > > > > It's not clear what should happen going forward. Let's say version = is > > > > incremented again. This then becomes challenging for downstreams to > > > > backport. > > > As all conditions are in the form of "if (s->version > X)" then incre= menting > > > version from 1 to 2 doesn't break any condition of "if (s->version > = 1)". > > > What is the challenge of backporting I'm missing? > > the challenge is figuring out which parts does version apply to. > > It might be easy if there's just code, harder if there's > > also data, etc. > You mean things such as the following? > s->some_field =3D (s->version > X) ? A : B; >=20 > True that it could be a bit more difficult to spot. >=20 > > > > > Will it suffice if I would just add documentation above "version"= property > > > > > on what is was the functionality in "version=3D=3D1"? > > > > > (Though, it's just easy to scan the vmport.c code for if's involv= ing > > > > > ">version"... "version" is more of an internal field for machine-= type > > > > > compatibility and not really meant to be used by user) > > > > >=20 > > > > > Which approach do you prefer? > > > > I just dislike versions, they are hard to maintain. > > > >=20 > > > > Individual ones is cleanest imho. Self-documenting. > > > I agree. That's the PVSCSI approach of compat_flags. Have many proper= ties > > > but each define bit in a compat_flags that specifies behavior. > > > The disadvantage it have is that it over-complicates code and introdu= ce many > > > properties that will never be used as it's just for internal binding = to > > > machine-type. > > > > But if not, I'd do something like "x-vmport-fixes" and > > > > set bits there for each bugfix. > > > Hmm this could a nice and simple approach. > > > Will it be OK then in this case to define "x-vmport-fixes" value in > > > hw_compat_4_2[] to a hard-coded value (e.g. "20") without directly en= coding > > > each individual bit via vmport.h constants? > > Well how are you going to check a specific flag then? > In the code itself I will have constants of course. > I meant just in hw_compat_4_2[] machine-type compat entry because the > bitmask value there should be specified as a string value. > >=20 > > > I will note though that it seems this "x-vmport-fixes" bitmap seems t= o be > > > the first of it's kind. But I'm OK with this approach. > So just to be clear before implementing your suggesting approach, this > doesn't bother you right? So it would be like this: { =09"x-vmport-fixes" : "0x7" /* VMPORT_FOO | VMPORT_BAR */ } I prefer DEFINE_PROP_BIT myself. But this version is not too terrible I think. --=20 MST