Re: [kvm-unit-tests PATCH] x86: vmx: Fix the check whether CMCI is supported

[Paolo Bonzini <pbonzini@redhat.com>]

On 09/10/19 13:27, Nadav Amit wrote:
> The logic of figuring out whether CMCI is supported is broken, causing
> the CMCI accessing tests to fail on Skylake bare-metal.
> 
> Determine whether CMCI is supported according to the maximum entries in
> the LVT as encoded in the APIC version register.
> 
> Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Nadav Amit <namit@vmware.com>
> ---
>  lib/x86/apic.h  |  7 +++++++
>  x86/vmx_tests.c | 10 +---------
>  2 files changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/lib/x86/apic.h b/lib/x86/apic.h
> index b5bf208..a7eff63 100644
> --- a/lib/x86/apic.h
> +++ b/lib/x86/apic.h
> @@ -70,6 +70,11 @@ static inline u32 x2apic_msr(u32 reg)
>  	return APIC_BASE_MSR + (reg >> 4);
>  }
>  
> +static inline bool apic_lvt_entry_supported(int idx)
> +{
> +	return GET_APIC_MAXLVT(apic_read(APIC_LVR)) >= idx;
> +}
> +
>  static inline bool x2apic_reg_reserved(u32 reg)
>  {
>  	switch (reg) {
> @@ -83,6 +88,8 @@ static inline bool x2apic_reg_reserved(u32 reg)
>  	case 0x3a0 ... 0x3d0:
>  	case 0x3f0:
>  		return true;
> +	case APIC_CMCI:
> +		return !apic_lvt_entry_supported(6);
>  	default:
>  		return false;
>  	}
> diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
> index f4b348b..0c710cd 100644
> --- a/x86/vmx_tests.c
> +++ b/x86/vmx_tests.c
> @@ -5863,11 +5863,6 @@ static u64 virt_x2apic_mode_nibble1(u64 val)
>  	return val & 0xf0;
>  }
>  
> -static bool is_cmci_enabled(void)
> -{
> -	return rdmsr(MSR_IA32_MCG_CAP) & BIT_ULL(10);
> -}
> -
>  static void virt_x2apic_mode_rd_expectation(
>  	u32 reg, bool virt_x2apic_mode_on, bool disable_x2apic,
>  	bool apic_register_virtualization, bool virtual_interrupt_delivery,
> @@ -5877,9 +5872,6 @@ static void virt_x2apic_mode_rd_expectation(
>  		!x2apic_reg_reserved(reg) &&
>  		reg != APIC_EOI;
>  
> -	if (reg == APIC_CMCI && !is_cmci_enabled())
> -		readable = false;
> -
>  	expectation->rd_exit_reason = VMX_VMCALL;
>  	expectation->virt_fn = virt_x2apic_mode_identity;
>  	if (virt_x2apic_mode_on && apic_register_virtualization) {
> @@ -5943,7 +5935,7 @@ static bool get_x2apic_wr_val(u32 reg, u64 *val)
>  		*val = apic_read(reg);
>  		break;
>  	case APIC_CMCI:
> -		if (!is_cmci_enabled())
> +		if (!apic_lvt_entry_supported(6))
>  			return false;
>  		*val = apic_read(reg);
>  		break;
> 

Applied, thanks.

Paolo