Vineeth Pillai <viremana@xxxxxxxxxxxxxxxxxxx> writes:
> Detect nested features exposed by Hyper-V if SVM is enabled.
>
> Signed-off-by: Vineeth Pillai <viremana@xxxxxxxxxxxxxxxxxxx>
> ---
> arch/x86/kernel/cpu/mshyperv.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 3546d3e21787..4d364acfe95d 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -325,9 +325,17 @@ static void __init ms_hyperv_init_platform(void)
> ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);
> }
>
> - if (ms_hyperv.hints & HV_X64_ENLIGHTENED_VMCS_RECOMMENDED) {
> + /*
> + * AMD does not need enlightened VMCS as VMCB is already a
> + * datastructure in memory.
Well, VMCS is also a structure in memory, isn't it? It's just that we
don't have a 'clean field' concept for it and we can't use normal memory
accesses.
> We need to get the nested
> + * features if SVM is enabled.
> + */
> + if (boot_cpu_has(X86_FEATURE_SVM) ||
> + ms_hyperv.hints & HV_X64_ENLIGHTENED_VMCS_RECOMMENDED) {
Do I understand correctly that we can just look at CPUID.0x40000000.EAX
and in case it is >= 0x4000000A we can read HYPERV_CPUID_NESTED_FEATURES
leaf? I'd suggest we do that intead then.
> ms_hyperv.nested_features =
> cpuid_eax(HYPERV_CPUID_NESTED_FEATURES);
> + pr_info("Hyper-V nested_features: 0x%x\n",
> + ms_hyperv.nested_features);
> }
>
> /*
--
Vitaly
