linux-kernel - RE: [PATCH v3 1/6] KVM: nVMX: Use hardware MSR bitmap

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Date:	Wed, 28 Jan 2015 08:05:23 +0000
From:	"Zhang, Yang Z" <yang.z.zhang@...el.com>
To:	Wincy Van <fanwenyi0529@...il.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	"gleb@...nel.org" <gleb@...nel.org>
CC:	"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 v3 1/6] KVM: nVMX: Use hardware MSR bitmap

Wincy Van wrote on 2015-01-24:
> When L2 is using x2apic, we can use virtualize x2apic mode to gain higher
> performance, especially in apicv case.
> 
> This patch also introduces nested_vmx_check_apicv_controls for the nested
> apicv patches.
> 
> Signed-off-by: Wincy Van <fanwenyi0529@...il.com>
> ---

...snip...

>  static void vmx_disable_intercept_for_msr(u32 msr, bool longmode_only)  {
>         if (!longmode_only)
> @@ -8344,7 +8394,68 @@ static int
> nested_vmx_check_msr_bitmap_controls(struct kvm_vcpu *vcpu,  static
> inline bool nested_vmx_merge_msr_bitmap(struct kvm_vcpu *vcpu,
>                                                struct vmcs12
> *vmcs12)  {
> -       return false;
> +       struct page *page;
> +       unsigned long *msr_bitmap;
> +
> +       if (!nested_cpu_has_virt_x2apic_mode(vmcs12))
> +               return false;
> +
> +       page = nested_get_page(vcpu, vmcs12->msr_bitmap);
> +       if (!page) {
> +               WARN_ON(1);
> +               return false;
> +       }
> +       msr_bitmap = (unsigned long *)kmap(page);
> +       if (!msr_bitmap) {
> +               nested_release_page_clean(page);
> +               WARN_ON(1);
> +               return false;
> +       }
> +
> +       memset(vmx_msr_bitmap_nested, 0xff, PAGE_SIZE);
> +
> +       if (nested_cpu_has_virt_x2apic_mode(vmcs12))
> +               /* TPR is allowed */
> +               nested_vmx_disable_intercept_for_msr(msr_bitmap,
> +                               vmx_msr_bitmap_nested,
> +                               APIC_BASE_MSR + (APIC_TASKPRI >>
> 4),
> +                               MSR_TYPE_R | MSR_TYPE_W);

I didn't understand what this function does? Per my understanding, you only need to set the (vmx_msr_bitmap_nested = vmcs01->msr_bitmap | vmcs12->msr_bitmap) and inject the nested vmexit to L1 if the bit in vmcs12->msr_bitmap is setting. Am I missing some patches?

Best regards,
Yang