On Wed, Jan 28, 2015 at 4:00 PM, Zhang, Yang Z <yang.z.zhang@xxxxxxxxx> wrote:
>> @@ -5812,13 +5813,18 @@ static __init int hardware_setup(void)
>> (unsigned long
>> *)__get_free_page(GFP_KERNEL);
>> if (!vmx_msr_bitmap_longmode_x2apic)
>> goto out4;
>> +
>> + vmx_msr_bitmap_nested = (unsigned long
>> *)__get_free_page(GFP_KERNEL);
>> + if (!vmx_msr_bitmap_nested)
>> + goto out5;
>> +
>
> Since the nested virtualization is off by default. It's better to allocate the page
> only when nested is true. Maybe adding the following check is better:
>
> if (nested) {
> vmx_msr_bitmap_nested = (unsigned long *)__get_free_page(GFP_KERNEL);
> if (!vmx_msr_bitmap_nested)
> goto out5;
> }
Agreed. Will do.
>
> ...snip...
>
>> +
>> +/*
>> + * Merge L0's and L1's MSR bitmap, return false to indicate that
>> + * we do not use the hardware.
>> + */
>> +static inline bool nested_vmx_merge_msr_bitmap(struct kvm_vcpu *vcpu,
>> + struct vmcs12
>> *vmcs12) {
>> + return false;
>> +}
>> +
>
> The following patches have nothing to do with the MSR control. Why leave the function empty here?
>
No. In patch "Enable nested virtualize x2apic mode", we will return
false if L1 disabled virt_x2apic_mode, then the hardware MSR-bitmap
control is disabled. This is faster than rebuilding the
vmx_msr_bitmap_nested.
This function returns false here to indicate that we do not use the
hardware. Since It is not only virtualize x2apic mode using this,
other features may use this either. I think it isn't suitable to
introduce this function in other patches.
> Best regards,
> Yang
>
>
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