linux-kernel - Re: [PATCH v4 2/6] KVM: nVMX: Enable nested virtualize x2apic mode

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Message-ID: <CACzj_yXbEirXExiC3p2m_zf9AGLYGKU5fLGHdizPN10eL4Q5Ug@mail.gmail.com>
Date:	Thu, 29 Jan 2015 11:53:28 +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>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	Wanpeng Li <wanpeng.li@...ux.intel.com>,
	Jan Kiszka <jan.kiszka@....de>
Subject: Re: [PATCH v4 2/6] KVM: nVMX: Enable nested virtualize x2apic mode

On Thu, Jan 29, 2015 at 10:54 AM, Zhang, Yang Z <yang.z.zhang@...el.com> wrote:
>> -8646,7 +8750,8 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu,
>> struct vmcs12 *vmcs12)
>>                         else
>>                                 vmcs_write64(APIC_ACCESS_ADDR,
>>
>> page_to_phys(vmx->nested.apic_access_page));
>> -               } else if
>> (vm_need_virtualize_apic_accesses(vmx->vcpu.kvm)) {
>> +               } else if (!(nested_cpu_has_virt_x2apic_mode(vmcs12)) &&
>> +
>> + (vm_need_virtualize_apic_accesses(vmx->vcpu.kvm))) {
>>                         exec_control |=
>
> You don't load L2's apic_page in your patch correctly when x2apic mode is used. Here is the right change for prepare_vmcs02()(maybe other place also need change too):
>
> @@ -8585,7 +8585,8 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
>                                 CPU_BASED_ACTIVATE_SECONDARY_CONTROLS))
>                         exec_control |= vmcs12->secondary_vm_exec_control;
>
> -               if (exec_control & SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES) {
> +               if (exec_control & (SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
> +                                   SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE)) {
>                         /*
>                          * If translation failed, no matter: This feature asks
>                          * to exit when accessing the given address, and if it
> @@ -8594,7 +8595,8 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
>                          */
>                         if (!vmx->nested.apic_access_page)
>                                 exec_control &=
> -                                 ~SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
> +                                 ~ (SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
> +                                    SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE);
>                         else
>                                 vmcs_write64(APIC_ACCESS_ADDR,
>                                   page_to_phys(vmx->nested.apic_access_page));
>

I think we don't need to do this, if L1 enables x2apic mode, we have
already checked that the
vmcs12->SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES is 0. "exec_control |=
vmcs12->secondary_vm_exec_control;" merged L1's settings, including
x2apic mode. the special case is vm_need_virtualize_apic_accesses, if
vm_need_virtualize_apic_accesses returns true, the
nested_cpu_has_virt_x2apic_mode will prevent us to set the apic access
bit.


Thanks,
Wincy
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