diff mbox

[2/5] KVM: x86: drop fpu_activate hook

Message ID 1408355431-115633-2-git-send-email-wanpeng.li@linux.intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Wanpeng Li Aug. 18, 2014, 9:50 a.m. UTC 
fpu_activate hook is introduced by commit 6b52d186 (KVM: Activate fpu on 
clts), however, there is no user currently, this patch drop it.

Reviewed-by: Yang Zhang <yang.z.zhang@intel.com>
Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
 arch/x86/include/asm/kvm_host.h | 1 -
 arch/x86/kvm/svm.c              | 1 -
 arch/x86/kvm/vmx.c              | 1 -
 3 files changed, 3 deletions(-)

Comments

Paolo Bonzini Aug. 18, 2014, 10:20 a.m. UTC | #1 
Il 18/08/2014 11:50, Wanpeng Li ha scritto:
> fpu_activate hook is introduced by commit 6b52d186 (KVM: Activate fpu on 
> clts), however, there is no user currently, this patch drop it.
> 
> Reviewed-by: Yang Zhang <yang.z.zhang@intel.com>
> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
> ---
>  arch/x86/include/asm/kvm_host.h | 1 -
>  arch/x86/kvm/svm.c              | 1 -
>  arch/x86/kvm/vmx.c              | 1 -
>  3 files changed, 3 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 5724601..b68f3e5 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -710,7 +710,6 @@ struct kvm_x86_ops {
>  	void (*cache_reg)(struct kvm_vcpu *vcpu, enum kvm_reg reg);
>  	unsigned long (*get_rflags)(struct kvm_vcpu *vcpu);
>  	void (*set_rflags)(struct kvm_vcpu *vcpu, unsigned long rflags);
> -	void (*fpu_activate)(struct kvm_vcpu *vcpu);
>  	void (*fpu_deactivate)(struct kvm_vcpu *vcpu);
>  
>  	void (*tlb_flush)(struct kvm_vcpu *vcpu);
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index ddf7427..1f49c86 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -4349,7 +4349,6 @@ static struct kvm_x86_ops svm_x86_ops = {
>  	.cache_reg = svm_cache_reg,
>  	.get_rflags = svm_get_rflags,
>  	.set_rflags = svm_set_rflags,
> -	.fpu_activate = svm_fpu_activate,
>  	.fpu_deactivate = svm_fpu_deactivate,
>  
>  	.tlb_flush = svm_flush_tlb,
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 71cbee5..2963303 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -8896,7 +8896,6 @@ static struct kvm_x86_ops vmx_x86_ops = {
>  	.cache_reg = vmx_cache_reg,
>  	.get_rflags = vmx_get_rflags,
>  	.set_rflags = vmx_set_rflags,
> -	.fpu_activate = vmx_fpu_activate,
>  	.fpu_deactivate = vmx_fpu_deactivate,
>  
>  	.tlb_flush = vmx_flush_tlb,
> 

Avi/Gleb, do you remember any particular reason for this?

Paolo
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Avi Kivity Aug. 18, 2014, 10:26 a.m. UTC | #2 
On 08/18/2014 01:20 PM, Paolo Bonzini wrote:
> Il 18/08/2014 11:50, Wanpeng Li ha scritto:
>> fpu_activate hook is introduced by commit 6b52d186 (KVM: Activate fpu on
>> clts), however, there is no user currently, this patch drop it.
>>
>> Reviewed-by: Yang Zhang <yang.z.zhang@intel.com>
>> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
>> ---
>>   arch/x86/include/asm/kvm_host.h | 1 -
>>   arch/x86/kvm/svm.c              | 1 -
>>   arch/x86/kvm/vmx.c              | 1 -
>>   3 files changed, 3 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>> index 5724601..b68f3e5 100644
>> --- a/arch/x86/include/asm/kvm_host.h
>> +++ b/arch/x86/include/asm/kvm_host.h
>> @@ -710,7 +710,6 @@ struct kvm_x86_ops {
>>   	void (*cache_reg)(struct kvm_vcpu *vcpu, enum kvm_reg reg);
>>   	unsigned long (*get_rflags)(struct kvm_vcpu *vcpu);
>>   	void (*set_rflags)(struct kvm_vcpu *vcpu, unsigned long rflags);
>> -	void (*fpu_activate)(struct kvm_vcpu *vcpu);
>>   	void (*fpu_deactivate)(struct kvm_vcpu *vcpu);
>>   
>>   	void (*tlb_flush)(struct kvm_vcpu *vcpu);
>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>> index ddf7427..1f49c86 100644
>> --- a/arch/x86/kvm/svm.c
>> +++ b/arch/x86/kvm/svm.c
>> @@ -4349,7 +4349,6 @@ static struct kvm_x86_ops svm_x86_ops = {
>>   	.cache_reg = svm_cache_reg,
>>   	.get_rflags = svm_get_rflags,
>>   	.set_rflags = svm_set_rflags,
>> -	.fpu_activate = svm_fpu_activate,
>>   	.fpu_deactivate = svm_fpu_deactivate,
>>   
>>   	.tlb_flush = svm_flush_tlb,
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index 71cbee5..2963303 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -8896,7 +8896,6 @@ static struct kvm_x86_ops vmx_x86_ops = {
>>   	.cache_reg = vmx_cache_reg,
>>   	.get_rflags = vmx_get_rflags,
>>   	.set_rflags = vmx_set_rflags,
>> -	.fpu_activate = vmx_fpu_activate,
>>   	.fpu_deactivate = vmx_fpu_deactivate,
>>   
>>   	.tlb_flush = vmx_flush_tlb,
>>
> Avi/Gleb, do you remember any particular reason for this?
>

IIRC (vaguely) if we expect the fpu to be used in the near future, we 
activate it eagerly so that we don't fault when it is used.

Prevents the sequence:

guest user: use fpu
#NM
host: reflect #NM to guest
guest kernel: CLTS
guest kernel: switch fpu state
#NM
host: switch fpu
guest kernel: switch fpu state (restarted)
guest user: use fpu (restarted)

Why was the user removed? Full-time eager fpu?
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Paolo Bonzini Aug. 18, 2014, 10:51 a.m. UTC | #3 
Il 18/08/2014 12:26, Avi Kivity ha scritto:
> 
> On 08/18/2014 01:20 PM, Paolo Bonzini wrote:
>> Il 18/08/2014 11:50, Wanpeng Li ha scritto:
>>> fpu_activate hook is introduced by commit 6b52d186 (KVM: Activate fpu on
>>> clts), however, there is no user currently, this patch drop it.
>>>
>>> Reviewed-by: Yang Zhang <yang.z.zhang@intel.com>
>>> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
>>> ---
>>>   arch/x86/include/asm/kvm_host.h | 1 -
>>>   arch/x86/kvm/svm.c              | 1 -
>>>   arch/x86/kvm/vmx.c              | 1 -
>>>   3 files changed, 3 deletions(-)
>>>
>>> diff --git a/arch/x86/include/asm/kvm_host.h
>>> b/arch/x86/include/asm/kvm_host.h
>>> index 5724601..b68f3e5 100644
>>> --- a/arch/x86/include/asm/kvm_host.h
>>> +++ b/arch/x86/include/asm/kvm_host.h
>>> @@ -710,7 +710,6 @@ struct kvm_x86_ops {
>>>       void (*cache_reg)(struct kvm_vcpu *vcpu, enum kvm_reg reg);
>>>       unsigned long (*get_rflags)(struct kvm_vcpu *vcpu);
>>>       void (*set_rflags)(struct kvm_vcpu *vcpu, unsigned long rflags);
>>> -    void (*fpu_activate)(struct kvm_vcpu *vcpu);
>>>       void (*fpu_deactivate)(struct kvm_vcpu *vcpu);
>>>         void (*tlb_flush)(struct kvm_vcpu *vcpu);
>>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>>> index ddf7427..1f49c86 100644
>>> --- a/arch/x86/kvm/svm.c
>>> +++ b/arch/x86/kvm/svm.c
>>> @@ -4349,7 +4349,6 @@ static struct kvm_x86_ops svm_x86_ops = {
>>>       .cache_reg = svm_cache_reg,
>>>       .get_rflags = svm_get_rflags,
>>>       .set_rflags = svm_set_rflags,
>>> -    .fpu_activate = svm_fpu_activate,
>>>       .fpu_deactivate = svm_fpu_deactivate,
>>>         .tlb_flush = svm_flush_tlb,
>>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>>> index 71cbee5..2963303 100644
>>> --- a/arch/x86/kvm/vmx.c
>>> +++ b/arch/x86/kvm/vmx.c
>>> @@ -8896,7 +8896,6 @@ static struct kvm_x86_ops vmx_x86_ops = {
>>>       .cache_reg = vmx_cache_reg,
>>>       .get_rflags = vmx_get_rflags,
>>>       .set_rflags = vmx_set_rflags,
>>> -    .fpu_activate = vmx_fpu_activate,
>>>       .fpu_deactivate = vmx_fpu_deactivate,
>>>         .tlb_flush = vmx_flush_tlb,
>>>
>> Avi/Gleb, do you remember any particular reason for this?
>>
> 
> IIRC (vaguely) if we expect the fpu to be used in the near future, we
> activate it eagerly so that we don't fault when it is used.
> 
> Prevents the sequence:
> 
> guest user: use fpu
> #NM
> host: reflect #NM to guest
> guest kernel: CLTS
> guest kernel: switch fpu state
> #NM
> host: switch fpu
> guest kernel: switch fpu state (restarted)
> guest user: use fpu (restarted)
> 
> Why was the user removed? Full-time eager fpu?

No, I mean any reason to keep the hooks.  In the meanwhile I found it myself:

commit 2d04a05bd7e93c13f13a82ac40de4065a99d069b
Author: Avi Kivity <avi@redhat.com>
Date:   Wed Apr 20 15:32:49 2011 +0300

    KVM: x86 emulator: emulate CLTS internally
    
    Avoid using ctxt->vcpu; we can do everything with ->get_cr() and ->set_cr().
    
    A side effect is that we no longer activate the fpu on emulated CLTS; but that
    should be very rare.
    
    Signed-off-by: Avi Kivity <avi@redhat.com>

vmx_fpu_activate and svm_fpu_activate are still called on #NM and CLTS, but
never from common code after the above patch.

Activation on CLTS is currently VMX only; I guess on AMD we could check the
decode assists' CR_VALID bit and instruction length to detect CLTS.

Paolo
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Paolo Bonzini Aug. 18, 2014, 10:52 a.m. UTC | #4 
Il 18/08/2014 11:50, Wanpeng Li ha scritto:
> fpu_activate hook is introduced by commit 6b52d186 (KVM: Activate fpu on 
> clts), however, there is no user currently, this patch drop it.
> 
> Reviewed-by: Yang Zhang <yang.z.zhang@intel.com>
> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
> ---
>  arch/x86/include/asm/kvm_host.h | 1 -
>  arch/x86/kvm/svm.c              | 1 -
>  arch/x86/kvm/vmx.c              | 1 -
>  3 files changed, 3 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 5724601..b68f3e5 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -710,7 +710,6 @@ struct kvm_x86_ops {
>  	void (*cache_reg)(struct kvm_vcpu *vcpu, enum kvm_reg reg);
>  	unsigned long (*get_rflags)(struct kvm_vcpu *vcpu);
>  	void (*set_rflags)(struct kvm_vcpu *vcpu, unsigned long rflags);
> -	void (*fpu_activate)(struct kvm_vcpu *vcpu);
>  	void (*fpu_deactivate)(struct kvm_vcpu *vcpu);
>  
>  	void (*tlb_flush)(struct kvm_vcpu *vcpu);
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index ddf7427..1f49c86 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -4349,7 +4349,6 @@ static struct kvm_x86_ops svm_x86_ops = {
>  	.cache_reg = svm_cache_reg,
>  	.get_rflags = svm_get_rflags,
>  	.set_rflags = svm_set_rflags,
> -	.fpu_activate = svm_fpu_activate,
>  	.fpu_deactivate = svm_fpu_deactivate,
>  
>  	.tlb_flush = svm_flush_tlb,
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 71cbee5..2963303 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -8896,7 +8896,6 @@ static struct kvm_x86_ops vmx_x86_ops = {
>  	.cache_reg = vmx_cache_reg,
>  	.get_rflags = vmx_get_rflags,
>  	.set_rflags = vmx_set_rflags,
> -	.fpu_activate = vmx_fpu_activate,
>  	.fpu_deactivate = vmx_fpu_deactivate,
>  
>  	.tlb_flush = vmx_flush_tlb,
> 

Applying shortly to kvm/queue, thanks.

Paolo
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Avi Kivity Aug. 18, 2014, 11:15 a.m. UTC | #5 
On 08/18/2014 01:51 PM, Paolo Bonzini wrote:
> Il 18/08/2014 12:26, Avi Kivity ha scritto:
>> On 08/18/2014 01:20 PM, Paolo Bonzini wrote:
>>> Il 18/08/2014 11:50, Wanpeng Li ha scritto:
>>>> fpu_activate hook is introduced by commit 6b52d186 (KVM: Activate fpu on
>>>> clts), however, there is no user currently, this patch drop it.
>>>>
>>>> Reviewed-by: Yang Zhang <yang.z.zhang@intel.com>
>>>> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
>>>> ---
>>>>    arch/x86/include/asm/kvm_host.h | 1 -
>>>>    arch/x86/kvm/svm.c              | 1 -
>>>>    arch/x86/kvm/vmx.c              | 1 -
>>>>    3 files changed, 3 deletions(-)
>>>>
>>>> diff --git a/arch/x86/include/asm/kvm_host.h
>>>> b/arch/x86/include/asm/kvm_host.h
>>>> index 5724601..b68f3e5 100644
>>>> --- a/arch/x86/include/asm/kvm_host.h
>>>> +++ b/arch/x86/include/asm/kvm_host.h
>>>> @@ -710,7 +710,6 @@ struct kvm_x86_ops {
>>>>        void (*cache_reg)(struct kvm_vcpu *vcpu, enum kvm_reg reg);
>>>>        unsigned long (*get_rflags)(struct kvm_vcpu *vcpu);
>>>>        void (*set_rflags)(struct kvm_vcpu *vcpu, unsigned long rflags);
>>>> -    void (*fpu_activate)(struct kvm_vcpu *vcpu);
>>>>        void (*fpu_deactivate)(struct kvm_vcpu *vcpu);
>>>>          void (*tlb_flush)(struct kvm_vcpu *vcpu);
>>>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>>>> index ddf7427..1f49c86 100644
>>>> --- a/arch/x86/kvm/svm.c
>>>> +++ b/arch/x86/kvm/svm.c
>>>> @@ -4349,7 +4349,6 @@ static struct kvm_x86_ops svm_x86_ops = {
>>>>        .cache_reg = svm_cache_reg,
>>>>        .get_rflags = svm_get_rflags,
>>>>        .set_rflags = svm_set_rflags,
>>>> -    .fpu_activate = svm_fpu_activate,
>>>>        .fpu_deactivate = svm_fpu_deactivate,
>>>>          .tlb_flush = svm_flush_tlb,
>>>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>>>> index 71cbee5..2963303 100644
>>>> --- a/arch/x86/kvm/vmx.c
>>>> +++ b/arch/x86/kvm/vmx.c
>>>> @@ -8896,7 +8896,6 @@ static struct kvm_x86_ops vmx_x86_ops = {
>>>>        .cache_reg = vmx_cache_reg,
>>>>        .get_rflags = vmx_get_rflags,
>>>>        .set_rflags = vmx_set_rflags,
>>>> -    .fpu_activate = vmx_fpu_activate,
>>>>        .fpu_deactivate = vmx_fpu_deactivate,
>>>>          .tlb_flush = vmx_flush_tlb,
>>>>
>>> Avi/Gleb, do you remember any particular reason for this?
>>>
>> IIRC (vaguely) if we expect the fpu to be used in the near future, we
>> activate it eagerly so that we don't fault when it is used.
>>
>> Prevents the sequence:
>>
>> guest user: use fpu
>> #NM
>> host: reflect #NM to guest
>> guest kernel: CLTS
>> guest kernel: switch fpu state
>> #NM
>> host: switch fpu
>> guest kernel: switch fpu state (restarted)
>> guest user: use fpu (restarted)
>>
>> Why was the user removed? Full-time eager fpu?
> No, I mean any reason to keep the hooks.

If there are no callers, I can't think of any.

> In the meanwhile I found it myself:
>
> commit 2d04a05bd7e93c13f13a82ac40de4065a99d069b
> Author: Avi Kivity <avi@redhat.com>
> Date:   Wed Apr 20 15:32:49 2011 +0300
>
>      KVM: x86 emulator: emulate CLTS internally
>      
>      Avoid using ctxt->vcpu; we can do everything with ->get_cr() and ->set_cr().
>      
>      A side effect is that we no longer activate the fpu on emulated CLTS; but that
>      should be very rare.
>      
>      Signed-off-by: Avi Kivity <avi@redhat.com>
>
> vmx_fpu_activate and svm_fpu_activate are still called on #NM and CLTS, but
> never from common code after the above patch.
>
> Activation on CLTS is currently VMX only; I guess on AMD we could check the
> decode assists' CR_VALID bit and instruction length to detect CLTS.


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diff mbox

Patch

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 5724601..b68f3e5 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -710,7 +710,6 @@  struct kvm_x86_ops {
 	void (*cache_reg)(struct kvm_vcpu *vcpu, enum kvm_reg reg);
 	unsigned long (*get_rflags)(struct kvm_vcpu *vcpu);
 	void (*set_rflags)(struct kvm_vcpu *vcpu, unsigned long rflags);
-	void (*fpu_activate)(struct kvm_vcpu *vcpu);
 	void (*fpu_deactivate)(struct kvm_vcpu *vcpu);
 
 	void (*tlb_flush)(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index ddf7427..1f49c86 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -4349,7 +4349,6 @@  static struct kvm_x86_ops svm_x86_ops = {
 	.cache_reg = svm_cache_reg,
 	.get_rflags = svm_get_rflags,
 	.set_rflags = svm_set_rflags,
-	.fpu_activate = svm_fpu_activate,
 	.fpu_deactivate = svm_fpu_deactivate,
 
 	.tlb_flush = svm_flush_tlb,
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 71cbee5..2963303 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8896,7 +8896,6 @@  static struct kvm_x86_ops vmx_x86_ops = {
 	.cache_reg = vmx_cache_reg,
 	.get_rflags = vmx_get_rflags,
 	.set_rflags = vmx_set_rflags,
-	.fpu_activate = vmx_fpu_activate,
 	.fpu_deactivate = vmx_fpu_deactivate,
 
 	.tlb_flush = vmx_flush_tlb,