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

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

[Zhao Liu]

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).
 
 QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs LGPL
 VGA BIOS.
-- 
2.34.1

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

[Philippe Mathieu-Daudé]

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

>   QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs LGPL
>   VGA BIOS.

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

[Zhao Liu]

Hi Philippe,

On Fri, Apr 12, 2024 at 11:57:35AM +0200, Philippe Mathieu-Daudé wrote:
> Date: Fri, 12 Apr 2024 11:57:35 +0200
> From: Philippe Mathieu-Daudé <philmd@linaro.org>
> Subject: Re: [PATCH-for-9.0?] docs: i386: pc: Update maximum CPU numbers
>  for PC Q35
> 
> > -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

Yes, I think there should be no need to mention older versions here?

Since the Q35's 4096 CPUs change will be stated in the v9.0 release, I
doubt we should synchronize the doc update (so I added the "for-v9.0?"
tag to throw this question out).

Thanks,
Zhao

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

[Michael S. Tsirkin]

On Fri, Apr 12, 2024 at 04:53:58PM +0800, 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>


Acked-by: Michael S. Tsirkin <mst@redhat.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).
>  
>  QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs LGPL
>  VGA BIOS.
> -- 
> 2.34.1

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

[Michael S. Tsirkin]

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.

> >   QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs LGPL
> >   VGA BIOS.

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

[Philippe Mathieu-Daudé]

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:

$ qemu-system-i386 -M pc-q35-2.8 -smp 666
qemu-system-i386: Invalid SMP CPUs 666. The max CPUs supported by 
machine 'pc-q35-2.8' is 288

$ qemu-system-i386 -M pc-q35-8.0 -smp 666
qemu-system-i386: Invalid SMP CPUs 666. The max CPUs supported by 
machine 'pc-q35-8.0' is 288

$ qemu-system-i386 -M pc-q35-9.0 -smp 666
Unexpected error in apic_common_set_id() at ../hw/intc/apic_common.c:447:
qemu-system-i386: APIC ID 255 requires x2APIC feature in CPU
Abort trap: 6

I'd rather at least:

"SMP is supported with up to 255 CPUs (and since v9.0: 4096 CPUs for PC 
Q35 machine)."

or:

"SMP is supported with up to 255 CPUs (and 4096 CPUs for PC Q35 machine 
since v9.0)."

>>>    QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs LGPL
>>>    VGA BIOS.
> 

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

[Daniel P. Berrangé]

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)


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 :|

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

[Daniel P. Berrangé]

On Tue, Jun 04, 2024 at 04:59:49PM +0800, Zhao Liu wrote:
> 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.

That's no problem at all. A followup patch is fine.

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 :|

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

[Zhao Liu]

On Mon, Jun 03, 2024 at 07:31:47PM +0200, Philippe Mathieu-Daudé wrote:
> Date: Mon, 3 Jun 2024 19:31:47 +0200
> From: Philippe Mathieu-Daudé <philmd@linaro.org>
> Subject: Re: [PATCH-for-9.0?] docs: i386: pc: Update maximum CPU numbers
>  for PC Q35
> 
> 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:
> 
> $ qemu-system-i386 -M pc-q35-2.8 -smp 666
> qemu-system-i386: Invalid SMP CPUs 666. The max CPUs supported by machine
> 'pc-q35-2.8' is 288
> 
> $ qemu-system-i386 -M pc-q35-8.0 -smp 666
> qemu-system-i386: Invalid SMP CPUs 666. The max CPUs supported by machine
> 'pc-q35-8.0' is 288
> 
> $ qemu-system-i386 -M pc-q35-9.0 -smp 666
> Unexpected error in apic_common_set_id() at ../hw/intc/apic_common.c:447:
> qemu-system-i386: APIC ID 255 requires x2APIC feature in CPU
> Abort trap: 6

For tcg, it needs to set x2apic=on in -cpu.

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

[Zhao Liu]

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

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

[Philippe Mathieu-Daudé]

On 4/6/24 10:54, Zhao Liu wrote:
> On Mon, Jun 03, 2024 at 07:31:47PM +0200, Philippe Mathieu-Daudé wrote:
>> Date: Mon, 3 Jun 2024 19:31:47 +0200
>> From: Philippe Mathieu-Daudé <philmd@linaro.org>
>> Subject: Re: [PATCH-for-9.0?] docs: i386: pc: Update maximum CPU numbers
>>   for PC Q35
>>
>> 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:
>>
>> $ qemu-system-i386 -M pc-q35-2.8 -smp 666
>> qemu-system-i386: Invalid SMP CPUs 666. The max CPUs supported by machine
>> 'pc-q35-2.8' is 288
>>
>> $ qemu-system-i386 -M pc-q35-8.0 -smp 666
>> qemu-system-i386: Invalid SMP CPUs 666. The max CPUs supported by machine
>> 'pc-q35-8.0' is 288
>>
>> $ qemu-system-i386 -M pc-q35-9.0 -smp 666
>> Unexpected error in apic_common_set_id() at ../hw/intc/apic_common.c:447:
>> qemu-system-i386: APIC ID 255 requires x2APIC feature in CPU
>> Abort trap: 6
> 
> For tcg, it needs to set x2apic=on in -cpu.

Thanks for clarifying. Using error_append_hint() is certainly
better than aborting or asking on the mailing list (from user
perspective) ;)

Regards,

Phil.

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

[Zhao Liu]

[snip]

> > > $ qemu-system-i386 -M pc-q35-9.0 -smp 666
> > > Unexpected error in apic_common_set_id() at ../hw/intc/apic_common.c:447:
> > > qemu-system-i386: APIC ID 255 requires x2APIC feature in CPU
> > > Abort trap: 6
> > 
> > For tcg, it needs to set x2apic=on in -cpu.
> 
> Thanks for clarifying. Using error_append_hint() is certainly
> better than aborting or asking on the mailing list (from user
> perspective) ;)

Good idea! Will improve this. ;-)