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Fri, 26 Sep 2025 12:39:59 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.175]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2E4C71800579; Fri, 26 Sep 2025 12:39:54 +0000 (UTC) Date: Fri, 26 Sep 2025 13:39:51 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Markus Armbruster Cc: Mark Cave-Ayland , imammedo@redhat.com, philmd@linaro.org, jdenemar@redhat.com, pbonzini@redhat.com, richard.henderson@linaro.org, eduardo@habkost.net, mst@redhat.com, marcel.apfelbaum@gmail.com, qemu-devel@nongnu.org Subject: Re: [PATCH v2 1/2] hw/i386/isapc.c: remove support for -cpu host and -cpu max Message-ID: References: <20250925160453.2025885-1-mark.caveayland@nutanix.com> <20250925160453.2025885-2-mark.caveayland@nutanix.com> <87wm5lo37q.fsf@pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87wm5lo37q.fsf@pond.sub.org> User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) BAYES_00=-1.9, DKIM_INVALID=0.1, DKIM_SIGNED=0.1, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, Sep 26, 2025 at 01:36:25PM +0200, Markus Armbruster wrote: > Mark Cave-Ayland writes: > > > Following recent discussions on the mailing list, it has been decided > > that instead of mapping -cpu host and -cpu max to a suitable 32-bit x86 CPU, > > it is preferable to disallow them and use the existing valid_cpu_types > > validation logic so that an error is returned to the user instead. > > > > Signed-off-by: Mark Cave-Ayland > > --- > > hw/i386/isapc.c | 27 --------------------------- > > 1 file changed, 27 deletions(-) > > > > diff --git a/hw/i386/isapc.c b/hw/i386/isapc.c > > index 44f4a44672..6c35a397df 100644 > > --- a/hw/i386/isapc.c > > +++ b/hw/i386/isapc.c > > @@ -41,31 +41,6 @@ static void pc_init_isa(MachineState *machine) > > DriveInfo *hd[MAX_IDE_BUS * MAX_IDE_DEVS]; > > int i; > > > > - /* > > - * There is a small chance that someone unintentionally passes "-cpu max" > > - * for the isapc machine, which will provide a much more modern 32-bit > > - * CPU than would be expected for an ISA-era PC. If the "max" cpu type has > > - * been specified, choose the "best" 32-bit cpu possible which we consider > > - * be the pentium3 (deliberately choosing an Intel CPU given that the > > - * default 486 CPU for the isapc machine is also an Intel CPU). > > - */ > > - if (!strcmp(machine->cpu_type, X86_CPU_TYPE_NAME("max"))) { > > - machine->cpu_type = X86_CPU_TYPE_NAME("pentium3"); > > - warn_report("-cpu max is invalid for isapc machine, using pentium3"); > > - } > > - > > - /* > > - * Similarly if someone unintentionally passes "-cpu host" for the isapc > > - * machine then display a warning and also switch to the "best" 32-bit > > - * cpu possible which we consider to be the pentium3. This is because any > > - * host CPU will already be modern than this, but it also ensures any > > - * newer CPU flags/features are filtered out for older guests. > > - */ > > - if (!strcmp(machine->cpu_type, X86_CPU_TYPE_NAME("host"))) { > > - machine->cpu_type = X86_CPU_TYPE_NAME("pentium3"); > > - warn_report("-cpu host is invalid for isapc machine, using pentium3"); > > - } > > - > > if (machine->ram_size > 3.5 * GiB) { > > error_report("Too much memory for this machine: %" PRId64 " MiB, " > > "maximum 3584 MiB", machine->ram_size / MiB); > > @@ -162,8 +137,6 @@ static void isapc_machine_options(MachineClass *m) > > X86_CPU_TYPE_NAME("pentium2"), > > X86_CPU_TYPE_NAME("pentium3"), > > X86_CPU_TYPE_NAME("qemu32"), > > - X86_CPU_TYPE_NAME("max"), > > - X86_CPU_TYPE_NAME("host"), > > NULL > > }; > > PCMachineClass *pcmc = PC_MACHINE_CLASS(m); > > This reverts the "smart" part of recent > > commit e1e2909f8e74051a34a044940f90d4650b6e784a > Author: Mark Cave-Ayland > Date: Thu Aug 28 12:09:44 2025 +0100 > > hw/i386/pc_piix.c: restrict isapc machine to 32-bit CPUs > > The isapc machine represents a legacy ISA PC with a 486 CPU. Whilst it is > possible to specify any CPU via -cpu on the command line, it makes no > sense to allow modern 64-bit CPUs to be used. > > Restrict the isapc machine to the available 32-bit CPUs, taking care to > handle the case where if a user inadvertently uses either -cpu max or > -cpu host then the "best" 32-bit CPU is used (in this case the pentium3). What is written here made sense from the POV of use of isapc with qemu-system-x86_64, but in qemu-system-i686, both 'max' and 'host' where already 32-bit CPUs IIUC. Both this original patch and the new patch block them from being used in qemu-system-i686 which feels wrong given the justification above. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|