Re: [Qemu-devel] kvm: "warning: host doesn't support requested feature: CPUID.01H:ECX.x2apic [bit 21]"

[Lan Tianyu]

2016-02-20 17:00 GMT+08:00 Paolo Bonzini <address@hidden>:
>
>
> ----- Original Message -----
>> From: "Jan Kiszka" <address@hidden>
>> To: "Eduardo Habkost" <address@hidden>, "Paolo Bonzini" <address@hidden>
>> Cc: "qemu-devel" <address@hidden>, "kvm" <address@hidden>
>> Sent: Saturday, February 20, 2016 9:09:32 AM
>> Subject: kvm: "warning: host doesn't support requested feature: 
>> CPUID.01H:ECX.x2apic [bit 21]"
>>
>> Hi all,
>>
>> I suppose 5120901a37 introduced this: qemu with kernel_irqchip=off now
>> generates these warnings, one per VCPU, during QEMU startup. Is the plan
>> to live with them until we finally have x2APIC emulation in userspace
>> (ie. also MSR vmexiting to there), or should we otherwise avoid it?
>
> I think it's a bug, x2apic should be auto-suppressed with kernel_irqchip=off.
>

The patch is to fix the issue.
------------------------------------->8----------------------------
>From 58f2a3a94c8e7bf9f3474bcafb6c59cc4f8bcbd9 Mon Sep 17 00:00:00 2001
From: Lan Tianyu <address@hidden>
Date: Sun, 15 Jul 2001 01:40:17 -0400
Subject: [PATCH] Qemu/KVM: Remove x2apic feature from CPU model when
 kernel_irqchip=off

x2apic feature is in the kvm_default_props and automatically added to all
CPU models when KVM is enabled regardless of kernel_irqchip=off. This will
trigger "warning: host doesn't support requested feature: CPUID.01H:
ECX.x2apic [bit 21]" when kernel_irqchip=off. This patch is to remove x2apic
feature when kernel_irqchip=off.

Signed-off-by: Lan Tianyu <address@hidden>
---
 target-i386/cpu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index 0d447b5..2ec7eb7 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -2105,6 +2105,9 @@ static void x86_cpu_load_def(X86CPU *cpu,
X86CPUDefinition *def, Error **errp)

     /* Special cases not set in the X86CPUDefinition structs: */
     if (kvm_enabled()) {
+           if (!kvm_irqchip_in_kernel())
+               x86_cpu_change_kvm_default("x2apic", "off");
+
         x86_cpu_apply_props(cpu, kvm_default_props);
     }

--
1.9.3