From: Xin Li <xin3.li@intel.com>

Do not virtualize FRED if FRED consistency checks fail.

Either on broken hardware, or when run KVM on top of another hypervisor
before the underlying hypervisor implements nested FRED correctly.

Suggested-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Tested-by: Shan Kang <shan.kang@intel.com>
---
 arch/x86/kvm/vmx/capabilities.h | 7 +++++++
 arch/x86/kvm/vmx/vmx.c          | 3 +++
 2 files changed, 10 insertions(+)

diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
index e8f3ad0f79ee..2962a3bb9747 100644
--- a/arch/x86/kvm/vmx/capabilities.h
+++ b/arch/x86/kvm/vmx/capabilities.h
@@ -400,6 +400,13 @@ static inline bool vmx_pebs_supported(void)
 	return boot_cpu_has(X86_FEATURE_PEBS) && kvm_pmu_cap.pebs_ept;
 }
 
+static inline bool cpu_has_vmx_fred(void)
+{
+	/* No need to check FRED VM exit controls. */
+	return boot_cpu_has(X86_FEATURE_FRED) &&
+		(vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_FRED);
+}
+
 static inline bool cpu_has_notify_vmexit(void)
 {
 	return vmcs_config.cpu_based_2nd_exec_ctrl &
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index efd2ad397ad2..9b4c30db911f 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -8001,6 +8001,9 @@ static __init void vmx_set_cpu_caps(void)
 		kvm_cpu_cap_check_and_set(X86_FEATURE_DTES64);
 	}
 
+	if (!cpu_has_vmx_fred())
+		kvm_cpu_cap_clear(X86_FEATURE_FRED);
+
 	if (!enable_pmu)
 		kvm_cpu_cap_clear(X86_FEATURE_PDCM);
 	kvm_caps.supported_perf_cap = vmx_get_perf_capabilities();
-- 
2.46.2

On Mon, Sep 30, 2024 at 10:00:48PM -0700, Xin Li (Intel) wrote:
> +static inline bool cpu_has_vmx_fred(void)
> +{
> +	/* No need to check FRED VM exit controls. */
> +	return boot_cpu_has(X86_FEATURE_FRED) &&

For your whole patchset:

s/boot_cpu_has/cpu_feature_enabled/g

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

On 11/26/2024 7:32 AM, Borislav Petkov wrote:
> On Mon, Sep 30, 2024 at 10:00:48PM -0700, Xin Li (Intel) wrote:
>> +static inline bool cpu_has_vmx_fred(void)
>> +{
>> +	/* No need to check FRED VM exit controls. */
>> +	return boot_cpu_has(X86_FEATURE_FRED) &&
> 
> For your whole patchset:
> 
> s/boot_cpu_has/cpu_feature_enabled/g
> 

Already done based on your reply to other patches.

There is a lot of boot_cpu_has() in arch/x86/kvm/, and someone needs to
replace them :-P

On Tue, Nov 26, 2024 at 10:53:17AM -0800, Xin Li wrote:
> Already done based on your reply to other patches.

Thx.

> There is a lot of boot_cpu_has() in arch/x86/kvm/, and someone needs to
> replace them :-P

There are such all over the tree and it'll happen eventually.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

On Mon, Sep 30, 2024 at 10:00:48PM -0700, Xin Li (Intel) wrote:
>From: Xin Li <xin3.li@intel.com>
>
>Do not virtualize FRED if FRED consistency checks fail.
>
>Either on broken hardware, or when run KVM on top of another hypervisor
>before the underlying hypervisor implements nested FRED correctly.
>
>Suggested-by: Chao Gao <chao.gao@intel.com>
>Signed-off-by: Xin Li <xin3.li@intel.com>
>Signed-off-by: Xin Li (Intel) <xin@zytor.com>
>Tested-by: Shan Kang <shan.kang@intel.com>

Reviewed-by: Chao Gao <chao.gao@intel.com>

one nit below,

>---
> arch/x86/kvm/vmx/capabilities.h | 7 +++++++
> arch/x86/kvm/vmx/vmx.c          | 3 +++
> 2 files changed, 10 insertions(+)
>
>diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
>index e8f3ad0f79ee..2962a3bb9747 100644
>--- a/arch/x86/kvm/vmx/capabilities.h
>+++ b/arch/x86/kvm/vmx/capabilities.h
>@@ -400,6 +400,13 @@ static inline bool vmx_pebs_supported(void)
> 	return boot_cpu_has(X86_FEATURE_PEBS) && kvm_pmu_cap.pebs_ept;
> }
> 
>+static inline bool cpu_has_vmx_fred(void)
>+{
>+	/* No need to check FRED VM exit controls. */

how about:

	/*
	 * setup_vmcs_config() guarantees FRED VM-entry/exit controls are
	 * either all set or none. So, no need to check FRED VM-exit controls.
	 */

It is better to call out the reason.

>+	return boot_cpu_has(X86_FEATURE_FRED) &&
>+		(vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_FRED);
>+}
>+

On 10/22/2024 1:48 AM, Chao Gao wrote:
> On Mon, Sep 30, 2024 at 10:00:48PM -0700, Xin Li (Intel) wrote:
>> From: Xin Li <xin3.li@intel.com>
>>
>> Do not virtualize FRED if FRED consistency checks fail.
>>
>> Either on broken hardware, or when run KVM on top of another hypervisor
>> before the underlying hypervisor implements nested FRED correctly.
>>
>> Suggested-by: Chao Gao <chao.gao@intel.com>
>> Signed-off-by: Xin Li <xin3.li@intel.com>
>> Signed-off-by: Xin Li (Intel) <xin@zytor.com>
>> Tested-by: Shan Kang <shan.kang@intel.com>
> 
> Reviewed-by: Chao Gao <chao.gao@intel.com>
> 
> one nit below,
> 
>> ---
>> arch/x86/kvm/vmx/capabilities.h | 7 +++++++
>> arch/x86/kvm/vmx/vmx.c          | 3 +++
>> 2 files changed, 10 insertions(+)
>>
>> diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
>> index e8f3ad0f79ee..2962a3bb9747 100644
>> --- a/arch/x86/kvm/vmx/capabilities.h
>> +++ b/arch/x86/kvm/vmx/capabilities.h
>> @@ -400,6 +400,13 @@ static inline bool vmx_pebs_supported(void)
>> 	return boot_cpu_has(X86_FEATURE_PEBS) && kvm_pmu_cap.pebs_ept;
>> }
>>
>> +static inline bool cpu_has_vmx_fred(void)
>> +{
>> +	/* No need to check FRED VM exit controls. */
> 
> how about:
> 
> 	/*
> 	 * setup_vmcs_config() guarantees FRED VM-entry/exit controls are
> 	 * either all set or none. So, no need to check FRED VM-exit controls.
> 	 */
> 
> It is better to call out the reason.
> 

make sense!