Re: [Qemu-devel] [PATCH 1/2] target-i386: disable LINT0 after reset

[Nadav Amit]

I don’t happen to have a similar platform. On regular qemu/kvm runs with
q35, I see APIC_LVT0 is set once to 0x8700 on the BSP - as expected:

 qemu-system-x86-19345 [011] d... 2583274.503018: kvm_entry: vcpu 0
 qemu-system-x86-19345 [011] d... 2583274.503019: kvm_exit: reason APIC_ACCESS 
rip 0x7ffb8288 info 1350 0
 qemu-system-x86-19345 [011] .... 2583274.503020: kvm_emulate_insn: 
0:7ffb8288:c7 05 50 03 e0 fe 00 87 00 00 (prot32)
 qemu-system-x86-19345 [011] .... 2583274.503021: kvm_mmio: mmio write len 4 
gpa 0xfee00350 val 0x8700
 qemu-system-x86-19345 [011] .... 2583274.503021: kvm_apic: apic_write 
APIC_LVT0 = 0x8700

If someone sends a trace ( http://www.linux-kvm.org/page/Tracing ) of the
failure, I would be happy to assist.

Nadav

Gerd Hoffmann <address@hidden> wrote:

> On Mi, 2015-09-16 at 07:23 +0200, Jan Kiszka wrote:
>> On 2015-09-15 23:19, Alex Williamson wrote:
>>> On Mon, 2015-04-13 at 02:32 +0300, Nadav Amit wrote:
>>>> Due to old Seabios bug, QEMU reenable LINT0 after reset. This bug is long 
>>>> gone
>>>> and therefore this hack is no longer needed.  Since it violates the
>>>> specifications, it is removed.
>>>> 
>>>> Signed-off-by: Nadav Amit <address@hidden>
>>>> ---
>>>> hw/intc/apic_common.c | 9 ---------
>>>> 1 file changed, 9 deletions(-)
>>> 
>>> Please see bug: https://bugs.launchpad.net/qemu/+bug/1488363
>>> 
>>> Is this bug perhaps not as long gone as we thought, or is there
>>> something else going on here?  Thanks,
>> 
>> I would say, someone needs to check if the SeaBIOS line that is supposed
>> to enable LINT0 is actually executed on one of the broken systems and,
>> if not, why not.
> 
> There is only one reason (beside miscompiling seabios with
> CONFIG_QEMU=n) why seabios would skip acpi initialization, and that is
> apic not being present according to cpuid:
> 
>    cpuid(1, &eax, &ebx, &ecx, &cpuid_features);
>    if (eax < 1 || !(cpuid_features & CPUID_APIC)) {
>        // No apic - only the main cpu is present.
> 
> https://www.kraxel.org/cgit/seabios/tree/src/fw/smp.c#n79
> 
> cheers,
>  Gerd
> 
> PS: coreboot tripped over this too, fixed just a few days ago.