diff mbox series

[v2,09/11] KVM: SVM: Add VNMI bit definition

Message ID 20221129193717.513824-10-mlevitsk@redhat.com
State New
Headers
Series SVM: vNMI (with my fixes) |

Commit Message

Maxim Levitsky Nov. 29, 2022, 7:37 p.m. UTC 
  From: Santosh Shukla <santosh.shukla@amd.com>

VNMI exposes 3 capability bits (V_NMI, V_NMI_MASK, and V_NMI_ENABLE) to
virtualize NMI and NMI_MASK, Those capability bits are part of
VMCB::intr_ctrl -
V_NMI(11) - Indicates whether a virtual NMI is pending in the guest.
V_NMI_MASK(12) - Indicates whether virtual NMI is masked in the guest.
V_NMI_ENABLE(26) - Enables the NMI virtualization feature for the guest.

When Hypervisor wants to inject NMI, it will set V_NMI bit, Processor
will clear the V_NMI bit and Set the V_NMI_MASK which means the Guest is
handling NMI, After the guest handled the NMI, The processor will clear
the V_NMI_MASK on the successful completion of IRET instruction Or if
VMEXIT occurs while delivering the virtual NMI.

To enable the VNMI capability, Hypervisor need to program
V_NMI_ENABLE bit 1.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Santosh Shukla <santosh.shukla@amd.com>
---
 arch/x86/include/asm/svm.h | 7 +++++++
 1 file changed, 7 insertions(+)

Comments

Sean Christopherson Jan. 31, 2023, 10:42 p.m. UTC | #1 
On Tue, Nov 29, 2022, Maxim Levitsky wrote:
> From: Santosh Shukla <santosh.shukla@amd.com>
> 
> VNMI exposes 3 capability bits (V_NMI, V_NMI_MASK, and V_NMI_ENABLE) to
> virtualize NMI and NMI_MASK, Those capability bits are part of
> VMCB::intr_ctrl -
> V_NMI(11) - Indicates whether a virtual NMI is pending in the guest.
> V_NMI_MASK(12) - Indicates whether virtual NMI is masked in the guest.
> V_NMI_ENABLE(26) - Enables the NMI virtualization feature for the guest.
> 
> When Hypervisor wants to inject NMI, it will set V_NMI bit, Processor
> will clear the V_NMI bit and Set the V_NMI_MASK which means the Guest is
> handling NMI, After the guest handled the NMI, The processor will clear
> the V_NMI_MASK on the successful completion of IRET instruction Or if
> VMEXIT occurs while delivering the virtual NMI.
> 
> To enable the VNMI capability, Hypervisor need to program
> V_NMI_ENABLE bit 1.
> 
> Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
> Signed-off-by: Santosh Shukla <santosh.shukla@amd.com>
> ---
>  arch/x86/include/asm/svm.h | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
> index cb1ee53ad3b189..26d6f549ce2b46 100644
> --- a/arch/x86/include/asm/svm.h
> +++ b/arch/x86/include/asm/svm.h
> @@ -203,6 +203,13 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
>  #define X2APIC_MODE_SHIFT 30
>  #define X2APIC_MODE_MASK (1 << X2APIC_MODE_SHIFT)
>  
> +#define V_NMI_PENDING_SHIFT 11
> +#define V_NMI_PENDING (1 << V_NMI_PENDING_SHIFT)
> +#define V_NMI_MASK_SHIFT 12
> +#define V_NMI_MASK (1 << V_NMI_MASK_SHIFT)

Argh, more KVM warts.  The existing INT_CTL defines all use "mask" in the name,
so looking at V_NMI_MASK in the context of other code reads "vNMI is pending",
not "vNMIs are blocked".

IMO, the existing _MASK terminology is the one that's wrong, but there's an absurd
amount of prior art in svm.h :-(

And the really annoying one is V_INTR_MASKING_MASK, which IIRC says "virtual INTR
masking is enabled", not "virtual INTRs are blocked".

So maybe call this V_NMI_BLOCKING_MASK?  And tack on _MASK too the others (even
though I agree it's ugly).

> +#define V_NMI_ENABLE_SHIFT 26
> +#define V_NMI_ENABLE (1 << V_NMI_ENABLE_SHIFT)

Hrm.  I think I would prefer to keep the defines ordered by bit position.  Knowing
that there's an enable bit isn't all that critical for understanding vNMI pending
and blocked.
Santosh Shukla Feb. 2, 2023, 9:42 a.m. UTC | #2 
On 2/1/2023 4:12 AM, Sean Christopherson wrote:
> On Tue, Nov 29, 2022, Maxim Levitsky wrote:
>> From: Santosh Shukla <santosh.shukla@amd.com>
>>
>> VNMI exposes 3 capability bits (V_NMI, V_NMI_MASK, and V_NMI_ENABLE) to
>> virtualize NMI and NMI_MASK, Those capability bits are part of
>> VMCB::intr_ctrl -
>> V_NMI(11) - Indicates whether a virtual NMI is pending in the guest.
>> V_NMI_MASK(12) - Indicates whether virtual NMI is masked in the guest.
>> V_NMI_ENABLE(26) - Enables the NMI virtualization feature for the guest.
>>
>> When Hypervisor wants to inject NMI, it will set V_NMI bit, Processor
>> will clear the V_NMI bit and Set the V_NMI_MASK which means the Guest is
>> handling NMI, After the guest handled the NMI, The processor will clear
>> the V_NMI_MASK on the successful completion of IRET instruction Or if
>> VMEXIT occurs while delivering the virtual NMI.
>>
>> To enable the VNMI capability, Hypervisor need to program
>> V_NMI_ENABLE bit 1.
>>
>> Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
>> Signed-off-by: Santosh Shukla <santosh.shukla@amd.com>
>> ---
>>  arch/x86/include/asm/svm.h | 7 +++++++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
>> index cb1ee53ad3b189..26d6f549ce2b46 100644
>> --- a/arch/x86/include/asm/svm.h
>> +++ b/arch/x86/include/asm/svm.h
>> @@ -203,6 +203,13 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
>>  #define X2APIC_MODE_SHIFT 30
>>  #define X2APIC_MODE_MASK (1 << X2APIC_MODE_SHIFT)
>>  
>> +#define V_NMI_PENDING_SHIFT 11
>> +#define V_NMI_PENDING (1 << V_NMI_PENDING_SHIFT)
>> +#define V_NMI_MASK_SHIFT 12
>> +#define V_NMI_MASK (1 << V_NMI_MASK_SHIFT)
> 
> Argh, more KVM warts.  The existing INT_CTL defines all use "mask" in the name,
> so looking at V_NMI_MASK in the context of other code reads "vNMI is pending",
> not "vNMIs are blocked".
> 
> IMO, the existing _MASK terminology is the one that's wrong, but there's an absurd
> amount of prior art in svm.h :-(
> 
> And the really annoying one is V_INTR_MASKING_MASK, which IIRC says "virtual INTR
> masking is enabled", not "virtual INTRs are blocked".
> 
> So maybe call this V_NMI_BLOCKING_MASK?  And tack on _MASK too the others (even
> though I agree it's ugly).
> 

Sure.

>> +#define V_NMI_ENABLE_SHIFT 26
>> +#define V_NMI_ENABLE (1 << V_NMI_ENABLE_SHIFT)
> 
> Hrm.  I think I would prefer to keep the defines ordered by bit position.  Knowing
> that there's an enable bit isn't all that critical for understanding vNMI pending
> and blocked.

Sure, Sean will include in V3.

Thanks,
Santosh
diff mbox series

Patch

diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
index cb1ee53ad3b189..26d6f549ce2b46 100644
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -203,6 +203,13 @@  struct __attribute__ ((__packed__)) vmcb_control_area {
 #define X2APIC_MODE_SHIFT 30
 #define X2APIC_MODE_MASK (1 << X2APIC_MODE_SHIFT)
 
+#define V_NMI_PENDING_SHIFT 11
+#define V_NMI_PENDING (1 << V_NMI_PENDING_SHIFT)
+#define V_NMI_MASK_SHIFT 12
+#define V_NMI_MASK (1 << V_NMI_MASK_SHIFT)
+#define V_NMI_ENABLE_SHIFT 26
+#define V_NMI_ENABLE (1 << V_NMI_ENABLE_SHIFT)
+
 #define LBR_CTL_ENABLE_MASK BIT_ULL(0)
 #define VIRTUAL_VMLOAD_VMSAVE_ENABLE_MASK BIT_ULL(1)