Patchwork [2/4] KVM: PPC: BOOK3S: PR: Doorbell support

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Submitter Aneesh Kumar K.V
Date June 5, 2014, 12:08 p.m.
Message ID <1401970085-14493-3-git-send-email-aneesh.kumar@linux.vnet.ibm.com>
Download mbox | patch
Permalink /patch/356324/
State New
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Comments

Aneesh Kumar K.V - June 5, 2014, 12:08 p.m.
We don't have SMT support yet, hence we should not find a doorbell
message generated

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 arch/powerpc/kvm/book3s_emulate.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
Alexander Graf - June 5, 2014, 12:21 p.m.
On 05.06.14 14:08, Aneesh Kumar K.V wrote:
> We don't have SMT support yet, hence we should not find a doorbell
> message generated
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> ---
>   arch/powerpc/kvm/book3s_emulate.c | 18 ++++++++++++++++++
>   1 file changed, 18 insertions(+)
>
> diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
> index 1bb16a59dcbc..d6c87d085182 100644
> --- a/arch/powerpc/kvm/book3s_emulate.c
> +++ b/arch/powerpc/kvm/book3s_emulate.c
> @@ -28,7 +28,9 @@
>   #define OP_19_XOP_RFI		50
>   
>   #define OP_31_XOP_MFMSR		83
> +#define OP_31_XOP_MSGSNDP	142
>   #define OP_31_XOP_MTMSR		146
> +#define OP_31_XOP_MSGCLRP	174
>   #define OP_31_XOP_MTMSRD	178
>   #define OP_31_XOP_MTSR		210
>   #define OP_31_XOP_MTSRIN	242
> @@ -303,6 +305,22 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
>   
>   			break;
>   		}
> +		case OP_31_XOP_MSGSNDP:
> +		{
> +			/*
> +			 * PR KVM still don't support SMT mode. So we should

still?

> +			 * not see a MSGSNDP/MSGCLRP used with PR KVM
> +			 */
> +			pr_info("KVM: MSGSNDP used in non SMT case\n");
> +			emulated = EMULATE_FAIL;

What would happen on an HV guest with only 1 thread that MSGSNDs to 
thread 0? Would the guest get an illegal instruction trap, a 
self-interrupt or would this be a simple nop?


Alex

> +			break;
> +		}
> +		case OP_31_XOP_MSGCLRP:
> +		{
> +			pr_info("KVM: MSGCLRP used in non SMT case\n");
> +			emulated = EMULATE_FAIL;
> +			break;
> +		}
>   		default:
>   			emulated = EMULATE_FAIL;
>   		}

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Alexander Graf - June 5, 2014, 12:23 p.m.
On 05.06.14 14:21, Alexander Graf wrote:
>
> On 05.06.14 14:08, Aneesh Kumar K.V wrote:
>> We don't have SMT support yet, hence we should not find a doorbell
>> message generated
>>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
>> ---
>>   arch/powerpc/kvm/book3s_emulate.c | 18 ++++++++++++++++++
>>   1 file changed, 18 insertions(+)
>>
>> diff --git a/arch/powerpc/kvm/book3s_emulate.c 
>> b/arch/powerpc/kvm/book3s_emulate.c
>> index 1bb16a59dcbc..d6c87d085182 100644
>> --- a/arch/powerpc/kvm/book3s_emulate.c
>> +++ b/arch/powerpc/kvm/book3s_emulate.c
>> @@ -28,7 +28,9 @@
>>   #define OP_19_XOP_RFI        50
>>     #define OP_31_XOP_MFMSR        83
>> +#define OP_31_XOP_MSGSNDP    142
>>   #define OP_31_XOP_MTMSR        146
>> +#define OP_31_XOP_MSGCLRP    174
>>   #define OP_31_XOP_MTMSRD    178
>>   #define OP_31_XOP_MTSR        210
>>   #define OP_31_XOP_MTSRIN    242
>> @@ -303,6 +305,22 @@ int kvmppc_core_emulate_op_pr(struct kvm_run 
>> *run, struct kvm_vcpu *vcpu,
>>                 break;
>>           }
>> +        case OP_31_XOP_MSGSNDP:
>> +        {
>> +            /*
>> +             * PR KVM still don't support SMT mode. So we should
>
> still?
>
>> +             * not see a MSGSNDP/MSGCLRP used with PR KVM
>> +             */
>> +            pr_info("KVM: MSGSNDP used in non SMT case\n");
>> +            emulated = EMULATE_FAIL;
>
> What would happen on an HV guest with only 1 thread that MSGSNDs to 
> thread 0? Would the guest get an illegal instruction trap, a 
> self-interrupt or would this be a simple nop?

What I'm trying to say here is that it's ok to treat it as illegal 
instructions, but then we don't need this patch :).


Alex

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Aneesh Kumar K.V - June 5, 2014, 3:55 p.m.
Alexander Graf <agraf@suse.de> writes:

> On 05.06.14 14:21, Alexander Graf wrote:
>>
>> On 05.06.14 14:08, Aneesh Kumar K.V wrote:
>>> We don't have SMT support yet, hence we should not find a doorbell
>>> message generated
>>>
>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
>>> ---
>>>   arch/powerpc/kvm/book3s_emulate.c | 18 ++++++++++++++++++
>>>   1 file changed, 18 insertions(+)
>>>
>>> diff --git a/arch/powerpc/kvm/book3s_emulate.c 
>>> b/arch/powerpc/kvm/book3s_emulate.c
>>> index 1bb16a59dcbc..d6c87d085182 100644
>>> --- a/arch/powerpc/kvm/book3s_emulate.c
>>> +++ b/arch/powerpc/kvm/book3s_emulate.c
>>> @@ -28,7 +28,9 @@
>>>   #define OP_19_XOP_RFI        50
>>>     #define OP_31_XOP_MFMSR        83
>>> +#define OP_31_XOP_MSGSNDP    142
>>>   #define OP_31_XOP_MTMSR        146
>>> +#define OP_31_XOP_MSGCLRP    174
>>>   #define OP_31_XOP_MTMSRD    178
>>>   #define OP_31_XOP_MTSR        210
>>>   #define OP_31_XOP_MTSRIN    242
>>> @@ -303,6 +305,22 @@ int kvmppc_core_emulate_op_pr(struct kvm_run 
>>> *run, struct kvm_vcpu *vcpu,
>>>                 break;
>>>           }
>>> +        case OP_31_XOP_MSGSNDP:
>>> +        {
>>> +            /*
>>> +             * PR KVM still don't support SMT mode. So we should
>>
>> still?
>>
>>> +             * not see a MSGSNDP/MSGCLRP used with PR KVM
>>> +             */
>>> +            pr_info("KVM: MSGSNDP used in non SMT case\n");
>>> +            emulated = EMULATE_FAIL;
>>
>> What would happen on an HV guest with only 1 thread that MSGSNDs to 
>> thread 0? Would the guest get an illegal instruction trap, a 
>> self-interrupt or would this be a simple nop?
>
> What I'm trying to say here is that it's ok to treat it as illegal 
> instructions, but then we don't need this patch :).
>

Agreed. I will verify whether it is treated as a nop. If so will send an
updated patch.

-aneesh

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Aneesh Kumar K.V - June 6, 2014, 9:28 a.m.
Alexander Graf <agraf@suse.de> writes:

> On 05.06.14 14:08, Aneesh Kumar K.V wrote:
>> We don't have SMT support yet, hence we should not find a doorbell
>> message generated
>>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
>> ---
>>   arch/powerpc/kvm/book3s_emulate.c | 18 ++++++++++++++++++
>>   1 file changed, 18 insertions(+)
>>
>> diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
>> index 1bb16a59dcbc..d6c87d085182 100644
>> --- a/arch/powerpc/kvm/book3s_emulate.c
>> +++ b/arch/powerpc/kvm/book3s_emulate.c
>> @@ -28,7 +28,9 @@
>>   #define OP_19_XOP_RFI		50
>>   
>>   #define OP_31_XOP_MFMSR		83
>> +#define OP_31_XOP_MSGSNDP	142
>>   #define OP_31_XOP_MTMSR		146
>> +#define OP_31_XOP_MSGCLRP	174
>>   #define OP_31_XOP_MTMSRD	178
>>   #define OP_31_XOP_MTSR		210
>>   #define OP_31_XOP_MTSRIN	242
>> @@ -303,6 +305,22 @@ int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
>>   
>>   			break;
>>   		}
>> +		case OP_31_XOP_MSGSNDP:
>> +		{
>> +			/*
>> +			 * PR KVM still don't support SMT mode. So we should
>
> still?
>
>> +			 * not see a MSGSNDP/MSGCLRP used with PR KVM
>> +			 */
>> +			pr_info("KVM: MSGSNDP used in non SMT case\n");
>> +			emulated = EMULATE_FAIL;
>
> What would happen on an HV guest with only 1 thread that MSGSNDs to 
> thread 0? Would the guest get an illegal instruction trap, a 
> self-interrupt or would this be a simple nop?
>

We do get a self-interrupt. I tried the below

tag = mfspr(SPRN_TIR) & 0x7f;
ppc_msgsnd(5, 0, tag);

And that results in doorbell exception. That implies we will have to
have full implementation of doorbell. You can drop patch 2 and 3 from
this series. I will rework them.

NOTE: This is not an issue for Linux guest, because we don't send ipi
to self. But to complete the emulation of msgsndp we will need to
emulate it properly.

-aneesh

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Patch

diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
index 1bb16a59dcbc..d6c87d085182 100644
--- a/arch/powerpc/kvm/book3s_emulate.c
+++ b/arch/powerpc/kvm/book3s_emulate.c
@@ -28,7 +28,9 @@ 
 #define OP_19_XOP_RFI		50
 
 #define OP_31_XOP_MFMSR		83
+#define OP_31_XOP_MSGSNDP	142
 #define OP_31_XOP_MTMSR		146
+#define OP_31_XOP_MSGCLRP	174
 #define OP_31_XOP_MTMSRD	178
 #define OP_31_XOP_MTSR		210
 #define OP_31_XOP_MTSRIN	242
@@ -303,6 +305,22 @@  int kvmppc_core_emulate_op_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
 
 			break;
 		}
+		case OP_31_XOP_MSGSNDP:
+		{
+			/*
+			 * PR KVM still don't support SMT mode. So we should
+			 * not see a MSGSNDP/MSGCLRP used with PR KVM
+			 */
+			pr_info("KVM: MSGSNDP used in non SMT case\n");
+			emulated = EMULATE_FAIL;
+			break;
+		}
+		case OP_31_XOP_MSGCLRP:
+		{
+			pr_info("KVM: MSGCLRP used in non SMT case\n");
+			emulated = EMULATE_FAIL;
+			break;
+		}
 		default:
 			emulated = EMULATE_FAIL;
 		}