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

DISCUSSION Jan Kiszka 4 participants 6 messages Feb 20, 2016 – Feb 25, 2016 KVM

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Jan Kiszka

author

2016-02-20 08:09 UTC #0 lore raw

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?

Thanks,
Jan

Paolo Bonzini

maintainer

2016-02-20 09:00 UTC #1 lore raw

----- Original Message -----

Quoted 6 lines

From: "Jan Kiszka" <[email protected]>
To: "Eduardo Habkost" <[email protected]>, "Paolo Bonzini" <[email protected]>
Cc: "qemu-devel" <[email protected]>, "kvm" <[email protected]>
Sent: Saturday, February 20, 2016 9:09:32 AM
Subject: kvm: "warning: host doesn't support requested feature: CPUID.01H:ECX.x2apic [bit 21]"

Quoted 6 lines

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.

Paolo

Eduardo Habkost

2016-02-22 21:40 UTC #2 lore raw

(CCing libvir-list)

Quoted 7 lines · Paolo Bonzini

----- Original Message -----
Quoted 6 lines
From: "Jan Kiszka" <[email protected]>
To: "Eduardo Habkost" <[email protected]>, "Paolo Bonzini" <[email protected]>
Cc: "qemu-devel" <[email protected]>, "kvm" <[email protected]>
Sent: Saturday, February 20, 2016 9:09:32 AM
Subject: kvm: "warning: host doesn't support requested feature: CPUID.01H:ECX.x2apic [bit 21]"

Quoted 8 lines

Quoted 6 lines
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.

My first reaction is to dislike the idea of adding yet another variable that affects the results of CPU models.

But considering that we are moving towards a design where libvirt must not assume or query any low-level detail from CPU models at all, maybe this won't be harmful.

Signature · 1 line

Eduardo

Lan Tianyu

2016-02-25 08:33 UTC #3 lore raw

In reply to Paolo Bonzini

2016-02-20 17:00 GMT+08:00 Paolo Bonzini <[email protected]>:

Quoted 9 lines

----- Original Message -----
Quoted 6 lines
From: "Jan Kiszka" <[email protected]>
To: "Eduardo Habkost" <[email protected]>, "Paolo Bonzini" <[email protected]>
Cc: "qemu-devel" <[email protected]>, "kvm" <[email protected]>
Sent: Saturday, February 20, 2016 9:09:32 AM
Subject: kvm: "warning: host doesn't support requested feature: CPUID.01H:ECX.x2apic [bit 21]"

Quoted 9 lines

Quoted 6 lines
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----------------------------

Quoted 1 line

From 58f2a3a94c8e7bf9f3474bcafb6c59cc4f8bcbd9 Mon Sep 17 00:00:00 2001

From: Lan Tianyu <[email protected]>
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 <[email protected]>

---
 target-i386/cpu.c | 3 +++
 1 file changed, 3 insertions(+)

target-i386/cpu.c +0 -0

index 0d447b5..2ec7eb7 100644
@@ -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

Jan Kiszka

author

2016-02-25 08:39 UTC #4 lore raw

Quoted 28 lines · Lan Tianyu

2016-02-20 17:00 GMT+08:00 Paolo Bonzini <[email protected]>:
Quoted 9 lines
----- Original Message -----
Quoted 6 lines
From: "Jan Kiszka" <[email protected]>
To: "Eduardo Habkost" <[email protected]>, "Paolo Bonzini" <[email protected]>
Cc: "qemu-devel" <[email protected]>, "kvm" <[email protected]>
Sent: Saturday, February 20, 2016 9:09:32 AM
Subject: kvm: "warning: host doesn't support requested feature: CPUID.01H:ECX.x2apic [bit 21]"
Quoted 9 lines
Quoted 6 lines
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 <[email protected]>
Date: Sun, 15 Jul 2001 01:40:17 -0400
Subject: [PATCH] Qemu/KVM: Remove x2apic feature from CPU model when
kernel_irqchip=off

Quoted 5 lines

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.

We know this, but it's probably worth to mention the underlying reason
here: userspace devices don't support x2APIC.

Quoted 22 lines

Signed-off-by Lan Tianyu <[email protected]>

---
 target-i386/cpu.c | 3 +++
 1 file changed, 3 insertions(+)

target-i386/cpu.c +3 -1

index 0d447b5..2ec7eb7 100644
@@ -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);
     }
 
--

Quoted 2 lines

1.9.3

Make sure to comply with the coding style (there is a checkpatch.pl also in QEMU). And please post as a new thread with proper subject, otherwise people (and tools) will not find your patch as such.

Jan

Lan Tianyu

2016-02-25 12:31 UTC #5 lore raw

2016-02-25 16:39 GMT+08:00 Jan Kiszka <[email protected]>:

Quoted 67 lines · Lan Tianyu

Quoted 28 lines
2016-02-20 17:00 GMT+08:00 Paolo Bonzini <[email protected]>:
Quoted 9 lines
----- Original Message -----
Quoted 6 lines
From: "Jan Kiszka" <[email protected]>
To: "Eduardo Habkost" <[email protected]>, "Paolo Bonzini" <[email protected]>
Cc: "qemu-devel" <[email protected]>, "kvm" <[email protected]>
Sent: Saturday, February 20, 2016 9:09:32 AM
Subject: kvm: "warning: host doesn't support requested feature: CPUID.01H:ECX.x2apic [bit 21]"
Quoted 9 lines
Quoted 6 lines
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 <[email protected]>
Date: Sun, 15 Jul 2001 01:40:17 -0400
Subject: [PATCH] Qemu/KVM: Remove x2apic feature from CPU model when
kernel_irqchip=off
Quoted 5 lines
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.
We know this, but it's probably worth to mention the underlying reason
here: userspace devices don't support x2APIC.
Quoted 22 lines
Signed-off-by Lan Tianyu <[email protected]>
---
 target-i386/cpu.c | 3 +++
 1 file changed, 3 insertions(+)
target-i386/cpu.c +3 -1
index 0d447b5..2ec7eb7 100644
@@ -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);
     }
 
--
Quoted 2 lines
1.9.3
Make sure to comply with the coding style (there is a checkpatch.pl also in QEMU). And please post as a new thread with proper subject, otherwise people (and tools) will not find your patch as such.

Quoted 1 line

Jan

Thanks for comments. Will update soon..

Signature · 2 lines

Best regards
Tianyu Lan