Re: [Xen-devel] Regression in Xen 4.7-rc1 - can't boot HVM guests with more than 64 vCPUS.

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, May 03, 2016 at 03:13:32PM -0400, Konrad Rzeszutek Wilk wrote:
> On Tue, May 3, 2016 at 12:55 PM, Konrad Rzeszutek Wilk
> <konrad@xxxxxxxxxx> wrote:
> > On Tue, May 3, 2016 at 12:47 PM, Konrad Rzeszutek Wilk
> > <konrad.wilk@xxxxxxxxxx> wrote:
> >>
> >> The host has 240 CPUs and the HVM guests config looks as follow:
> >>
> >> -bash-4.1# cat /hvm.cfg
> >> memory=64000
> 
> You can also make this 1024.
> 
> And on another machine (which only has 4 physical CPUs) I got some
> date when trying starting this guest. The xl dmesg:reports
> 
> (XEN) HVM1 save: CPU
> (XEN) HVM1 save: PIC
> (XEN) HVM1 save: IOAPIC
> (XEN) HVM1 save: LAPIC
> (XEN) HVM1 save: LAPIC_REGS
> (XEN) HVM1 save: PCI_IRQ
> (XEN) HVM1 save: ISA_IRQ
> (XEN) HVM1 save: PCI_LINK
> (XEN) HVM1 save: PIT
> (XEN) HVM1 save: RTC
> (XEN) HVM1 save: HPET
> (XEN) HVM1 save: PMTIMER
> (XEN) HVM1 save: MTRR
> (XEN) HVM1 save: VIRIDIAN_DOMAIN
> (XEN) HVM1 save: CPU_XSAVE
> (XEN) HVM1 save: VIRIDIAN_VCPU
> (XEN) HVM1 save: VMCE_VCPU
> (XEN) HVM1 save: TSC_ADJUST
> (XEN) HVM1 restore: CPU 0

This is expected, ATM in order to set a HVM guest CPU context libxc first 
saves the current context (mainly in order to get a proper save context 
header), then it modifies the CPU registers and restores only the CPU 
context with the desired initial state. I don't expect this to affect the 
ioreq servers, but don't take my word for granted ;).

Roger.

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