linux-kernel - Re: [PATCH 2/5] KVM: nVMX: Enable nested virtualize x2apic mode.

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Date:	Wed, 21 Jan 2015 18:16:14 +0800
From:	Wincy Van <fanwenyi0529@...il.com>
To:	"Zhang, Yang Z" <yang.z.zhang@...el.com>
Cc:	Paolo Bonzini <pbonzini@...hat.com>,
	"gleb@...nel.org" <gleb@...nel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Wanpeng Li <wanpeng.li@...ux.intel.com>,
	Jan Kiszka <jan.kiszka@....de>
Subject: Re: [PATCH 2/5] KVM: nVMX: Enable nested virtualize x2apic mode.

On Wed, Jan 21, 2015 at 4:35 PM, Zhang, Yang Z <yang.z.zhang@...el.com> wrote:
> Wincy Van wrote on 2015-01-16:
>> When L2 is using x2apic, we can use virtualize x2apic mode to gain higher
>> performance.
>>
>> This patch also introduces nested_vmx_check_apicv_controls for the nested
>> apicv patches.
>>
>> Signed-off-by: Wincy Van <fanwenyi0529@...il.com>
>
> To enable x2apic, should you to consider the behavior changes to rdmsr and wrmsr. I didn't see your patch do it. Is it correct?

Yes, indeed, I've not noticed that kvm handle nested msr bitmap
manually, the next version will fix this.

> BTW, this patch has nothing to do with APICv, it's better to not use x2apic here and change to apicv in following patch.

Do you mean that we should split this patch from the apicv patch set?

>
>> ---
>>  arch/x86/kvm/vmx.c |   49
>> ++++++++++++++++++++++++++++++++++++++++++++++++-
>>  1 files changed, 48 insertions(+), 1 deletions(-)
>>
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 954dd54..10183ee
>> 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -1134,6 +1134,11 @@ static inline bool nested_cpu_has_xsaves(struct
>> vmcs12 *vmcs12)
>>                 vmx_xsaves_supported();
>>  }
>>
>> +static inline bool nested_cpu_has_virt_x2apic_mode(struct vmcs12
>> +*vmcs12) {
>> +       return nested_cpu_has2(vmcs12,
>> +SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE);
>> +}
>> +
>>  static inline bool is_exception(u32 intr_info)  {
>>         return (intr_info & (INTR_INFO_INTR_TYPE_MASK |
>> INTR_INFO_VALID_MASK)) @@ -2426,6 +2431,7 @@ static void
>> nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
>>         vmx->nested.nested_vmx_secondary_ctls_low = 0;
>>         vmx->nested.nested_vmx_secondary_ctls_high &=
>>                 SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
>> +               SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE |
>>                 SECONDARY_EXEC_WBINVD_EXITING |
>>                 SECONDARY_EXEC_XSAVES;
>>
>> @@ -7333,6 +7339,9 @@ static bool nested_vmx_exit_handled(struct
>> kvm_vcpu *vcpu)
>>         case EXIT_REASON_APIC_ACCESS:
>>                 return nested_cpu_has2(vmcs12,
>>
>> SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES);
>> +       case EXIT_REASON_APIC_WRITE:
>> +               /* apic_write should exit unconditionally. */
>> +               return 1;
>
> APIC_WRITE vmexit is introduced by APIC register virtualization not virtualize x2apic. Move it to next patch.

Agreed, will do.

Thanks,

Wincy
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