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 <phi...@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....@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....@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.