On 3/1/2016 10:00 PM, Eduardo Habkost wrote:
On Mon, Feb 29, 2016 at 10:56:04AM +0800, Lan Tianyu wrote:
On 2016年02月27日 03:54, Eduardo Habkost wrote:
On Thu, Feb 25, 2016 at 11:15:12PM +0800, Lan Tianyu wrote:
x2apic feature is in the kvm_default_props and automatically added to all
CPU models when KVM is enabled. But userspace devices don't support x2apic
which can't be enabled without the in-kernel irqchip. It will trigger
warning of "host doesn't support requested feature: CPUID.01H:ECX.x2apic
[bit 21]" when kernel_irqchip is off. This patch is to fix it via removing
x2apic feature when kernel_irqchip is off.
Signed-off-by: Lan Tianyu <tianyu.lan@xxxxxxxxx>
---
target-i386/cpu.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index c78f824..298fb62 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -2125,6 +2125,10 @@ 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");
This should be NULL instead of "off".
I tried "NULL" before. But some cpus modules(E,G SandyBridge,
IvyBridge, haswell) already have x2apic feature in their default
features of struct X86CPUDefinition, passing "NULL" is not to add x2apic
feature to the cpu module and will not help to remove x2apic feature for
these cpu modules. So I changed "NULL" to "off".
In this case, I suggest we remove x2apic from these CPU models to
avoid confusion, as the presence of the flag in the table makes
no difference at all (this can be done in a separate patch).
If we do that, NULL and "off" would have the same results, but
NULL is clearer, IMO. NULL simply disables the KVM-specific hack
(so we don't touch the property anymore), but "off" adds a new
TCG-specific hack. I will submit that as a follow-up patch.
Yes, that sounds reasonable. Thanks for your review.
Reviewed-by: Eduardo Habkost <ehabkost@xxxxxxxxxx>
Otherwise, the warning will
be disabled if using "-cpu ...,+x2apic".
kvm_arch_get_supported_cpuid() always returns no x2apic support when
kernel_irqchip is off and so it still triggers warning with "-cpu
...,+x2apic".
#qemu-system-x86_64 -cpu qemu64,+x2apic -machine kernel-irqchip=off
warning: TCG doesn't support requested feature: CPUID.01H:ECX.x2apic
[bit 21]
You are right. The +x2apic flag is applied after
x86_cpu_load_def() runs. My mistake.
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