Re: [Xen-devel] [PATCH V6] vm_event: Allow subscribing to write events for specific MSR-s

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Razvan Cojocaru [mailto:rcojocaru@xxxxxxxxxxxxxxx]
> Sent: Wednesday, April 27, 2016 3:48 PM
> +
> +static void *monitor_bitmap_for_msr(struct domain *d, u32 *msr)
> +{
> +    ASSERT(d->arch.monitor_msr_bitmap && msr);
> +
> +    switch ( *msr )
> +    {
> +    case 0 ... 0x1fff:
> +        BUILD_BUG_ON(ARRAY_SIZE(d->arch.monitor_msr_bitmap->low) * 8 <
> 0x1fff);
> +        return &d->arch.monitor_msr_bitmap->low;
> +
> +    case 0x40000000 ... 0x40001fff:
> +        BUILD_BUG_ON(
> +            ARRAY_SIZE(d->arch.monitor_msr_bitmap->hypervisor) * 8 < 0x1fff);
> +        *msr &= 0x1fff;
> +        return &d->arch.monitor_msr_bitmap->hypervisor;

I think we shouldn't change '*msr' directly here. Since later, 

> +
> +    case 0xc0000000 ... 0xc0001fff:
> +        BUILD_BUG_ON(ARRAY_SIZE(d->arch.monitor_msr_bitmap->high) * 8 <
> 0x1fff);
> +        *msr &= 0x1fff;
> +        return &d->arch.monitor_msr_bitmap->high;
> +
> +    default:
> +        return NULL;
> +    }
> +}
> +
> +static int monitor_enable_msr(struct domain *d, u32 msr)
> +{
> +    u32 *bitmap;
> +
> +    if ( !d->arch.monitor_msr_bitmap )
> +        return -ENXIO;
> +
> +    bitmap = monitor_bitmap_for_msr(d, &msr);
> +
> +    if ( !bitmap )
> +        return -EINVAL;
> +
> +    __set_bit(msr, bitmap);
> +
> +    hvm_enable_msr_interception(d, msr);

Here the original msr value is expected.

Thanks
Kevin

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