On Wed, May 27, 2020 at 10:01:21AM +0000, Anup Patel wrote: > > > > -----Original Message----- > > From: Daniel P. Berrangé <berra...@redhat.com> > > Sent: 27 May 2020 15:21 > > To: Anup Patel <anup.pa...@wdc.com> > > Cc: Eduardo Habkost <ehabk...@redhat.com>; Marcel Apfelbaum > > <marcel.apfelb...@gmail.com>; Peter Maydell <peter.mayd...@linaro.org>; > > Palmer Dabbelt <pal...@dabbelt.com>; Alistair Francis > > <alistair.fran...@wdc.com>; Sagar Karandikar <sag...@eecs.berkeley.edu>; > > Atish Patra <atish.pa...@wdc.com>; qemu-ri...@nongnu.org; qemu- > > de...@nongnu.org; Anup Patel <a...@brainfault.org> > > Subject: Re: [PATCH v2 1/5] hw: Add sockets_specified field in CpuTopology > > > > On Wed, May 27, 2020 at 09:48:39AM +0000, Anup Patel wrote: > > > > > > > > > > -----Original Message----- > > > > From: Daniel P. Berrangé <berra...@redhat.com> > > > > Sent: 27 May 2020 14:16 > > > > To: Anup Patel <anup.pa...@wdc.com> > > > > Cc: Eduardo Habkost <ehabk...@redhat.com>; Marcel Apfelbaum > > > > <marcel.apfelb...@gmail.com>; Peter Maydell > > > > <peter.mayd...@linaro.org>; Palmer Dabbelt <pal...@dabbelt.com>; > > > > Alistair Francis <alistair.fran...@wdc.com>; Sagar Karandikar > > > > <sag...@eecs.berkeley.edu>; Atish Patra <atish.pa...@wdc.com>; > > > > qemu-ri...@nongnu.org; qemu- de...@nongnu.org; Anup Patel > > > > <a...@brainfault.org> > > > > Subject: Re: [PATCH v2 1/5] hw: Add sockets_specified field in > > > > CpuTopology > > > > > > > > On Wed, May 27, 2020 at 11:12:22AM +0530, Anup Patel wrote: > > > > > When "sockets" sub-option of "-smp" option is not specified, the > > > > > smp_parse() function will assume one CPU per-socket and set the > > > > > number of sockets equal to number of CPUs. > > > > > > > > > > This is counter-intuitive and we should allow machine emulation to > > > > > decide default number of sockets when "sockets" sub-option is not > > > > > specified. > > > > > > > > I don't agree with this. Having the semantics of the -smp option be > > > > the same across all targets/machines *is* intuitive. Changing > > > > semantics of -smp per- machine will create a worse experiance for > > > > people configuring QEMU as the configuration will mean different things > > depending on the machine choce. > > > > > > Okay then why don't we default to sockets=1 in smp_parse() when "sockets" > > > sub-options is not specified ?? This will make it uniform across machines. > > > > > > Is there a reason to by default have sockets=max_cpus ?? > > > > IIUC both of these questions are due to backwards compatibility with pre- > > existing QEMU versions. > > I see that hw/x86/pc.c implements it's own smp_parse() callback. > Can we take that route ?? > > We need to have sockets=1 by default for RISC-V machines because > each socket has it's own interrupt controller and other peripherals.
I guess the fact that smp_parse() exists as a callback pretty much says that allowing machine type overrides of default semantics is permitted. So yeah, using a smp_parse callback seems reasonable. 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 :|
