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

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Date:	Wed, 21 Jan 2015 11:25:10 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Wincy Van <fanwenyi0529@...il.com>,
	"Zhang, Yang Z" <yang.z.zhang@...el.com>
CC:	"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 21/01/2015 11:16, Wincy Van wrote:
> 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?

I think it's okay to keep it in the same patchset, but you can put it first.

Paolo

> 
>>
>>> ---
>>>  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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