Re: Assertion '!is_idle_vcpu(v)' failed after 'Remove fully_eager_fpu' commit on EFI

[Jan Beulich <jbeulich@xxxxxxxx>]

On 12.06.2026 16:18, Andrew Cooper wrote:
> On 12/06/2026 3:11 pm, Marek Marczykowski-Górecki wrote:
>> On Fri, Jun 12, 2026 at 03:53:49PM +0200, Anthony PERARD wrote:
>>> Hi,
>>>
>>> Since commit dba44e051209 ("x86: Remove fully_eager_fpu"), I can't boot
>>> a machine and get assertion '!is_idle_vcpu(v)' failed instead. It's
>>> netbooted and EFI.
>>>
>>> Xen call trace:
>>>    [<ffff82d04033da2c>] R vcpu_save_fpu+0x65/0xdc
>>>    [<ffff82d04029c5c4>] S efi_rs_enter+0x37/0x16a
>>>    [<ffff82d04029c7e3>] F efi_get_time+0x19/0xb2
>>>    [<ffff82d04047cbf0>] F init_xen_time+0x1e3/0x2b4
>>>    [<ffff82d040477a49>] F __start_xen+0x1d71/0x24b8
>>>    [<ffff82d0402043e7>] F __high_start+0xb7/0xc0
>>>
>>> Assertion '!is_idle_vcpu(v)' failed at arch/x86/i387.c:195
>>>
>>> A few more lines from Xen:
>>>     CPU Vendor: Intel, Family 6 (0x6), Model 86 (0x56), Stepping 3 (raw 
>>> 00050663)
>>>     Bootloader: GRUB 2.06
>>>     [...]
>>>     Enabling APIC mode.  Using 2 I/O APICs
>>>     ENABLING IO-APIC IRQs
>>>      -> Using old ACK method
>>>      ..TIMER: vector=0xF0 apic1=0 pin1=2 apic2=-1 pin2=-1
>>>     TSC deadline timer enabled
>>>     Assertion '!is_idle_vcpu(v)' failed at arch/x86/i387.c:195
>>>
>>> Commit this Xen is built from: 50936ea05660.
>> Interesting, the efi_get_time() way is nowadays a fallback if cmos one
>> isn't advertised. Can you try adding `cmos-rtc-probe`?
>>
>> Anyway, surely it shouldn't crash... The commit you mentioned has "No
>> functional change intended", but well...
> 
> Well, no intended change.  It was a very big patch.
> 
> Nothing should ever be using efi_get_time().  It's unusable (i.e.
> crashing) on hundreds of millions of machines.
> 
> So, while we obviously do need to fix the assertion, this is "only"
> collateral damage from having fallen into the efi_get_time() path in the
> first place.  That wants investigating too.

Perhaps a reduced-hardware system with ACPI_FADT_NO_CMOS_RTC set? On such
systems efi_get_time() would better work properly.

Jan