Re: [PATCH-for-9.0?] docs: i386: pc: Update maximum CPU numbers for PC Q35

[Zhao Liu <zhao1.liu@intel.com>]

Hi Michael, Daniel, and Philippe,

On Mon, Jun 03, 2024 at 06:39:19PM +0100, Daniel P. Berrangé wrote:
> Date: Mon, 3 Jun 2024 18:39:19 +0100
> From: "Daniel P. Berrangé" <berrange@redhat.com>
> Subject: Re: [PATCH-for-9.0?] docs: i386: pc: Update maximum CPU numbers
>  for PC Q35
> 
> On Mon, Jun 03, 2024 at 07:31:47PM +0200, Philippe Mathieu-Daudé wrote:
> > Hi Michael,
> > 
> > On 2/6/24 15:30, Michael S. Tsirkin wrote:
> > > On Fri, Apr 12, 2024 at 11:57:35AM +0200, Philippe Mathieu-Daudé wrote:
> > > > Hi Zhao,
> > > > 
> > > > On 12/4/24 10:53, Zhao Liu wrote:
> > > > > From: Zhao Liu <zhao1.liu@intel.com>
> > > > > 
> > > > > Commit e4e98c7eebfa ("pc: q35: Bump max_cpus to 4096 vcpus") increases
> > > > > the supported CPUs for PC Q35 machine.
> > > > > 
> > > > > Update maximum CPU numbers for PC Q35 in the document.
> > > > > 
> > > > > Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
> > > > > ---
> > > > >    docs/system/target-i386-desc.rst.inc | 2 +-
> > > > >    1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > 
> > > > > diff --git a/docs/system/target-i386-desc.rst.inc b/docs/system/target-i386-desc.rst.inc
> > > > > index 5ebbcda9db4c..319e540573d3 100644
> > > > > --- a/docs/system/target-i386-desc.rst.inc
> > > > > +++ b/docs/system/target-i386-desc.rst.inc
> > > > > @@ -36,7 +36,7 @@ The QEMU PC System emulator simulates the following peripherals:
> > > > >    -  PCI UHCI, OHCI, EHCI or XHCI USB controller and a virtual USB-1.1
> > > > >       hub.
> > > > > -SMP is supported with up to 255 CPUs.
> > > > > +SMP is supported with up to 255 CPUs (and 4096 CPUs for PC Q35 machine).
> > > > 
> > > > This comment is not accurate since a while, IIUC:
> > > > 
> > > > Up to q35-2.7: 255
> > > > q35-2.8: 288
> > > > q35-8.0+: 1024
> > > > q35-9.0: 4096
> > > 
> > > 
> > > What are you saying here, Philippe? I don't think compat
> > > machine types matter enough to bother with more detail.
> > 
> > My point is I find this description confusing w.r.t. how QEMU behaves:
> 
>   snip
> 
> I think the docs should simply avoid mentioning any limit at all. ie
> 
>    -SMP is supported with up to 255 CPUs.
>    +SMP is supported with a large number of virtual CPUs (upper limit is
>     configuration dependent)

I agree, the limit may also be different for different scenarios, and it
is not appropriate to describe it in detail.

Sorry I forgot that this patch has been merged in by Thomas for me
(838f82468a12), and I can modify it with a new patch based on Daniel's
suggestion.

Thanks,
Zhao