Patchwork [v3,2/8] KVM: arm64: Rework detection of SVE, !VHE systems

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Submitter Marc Zyngier
Date Dec. 6, 2018, 5:31 p.m.
Message ID <20181206173126.139877-3-marc.zyngier@arm.com>
Download mbox | patch
Permalink /patch/674443/
State New
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Comments

Marc Zyngier - Dec. 6, 2018, 5:31 p.m.
An SVE system is so far the only case where we mandate VHE. As we're
starting to grow this requirements, let's slightly rework the way we
deal with that situation, allowing for easy extension of this check.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
 arch/arm/include/asm/kvm_host.h   | 2 +-
 arch/arm64/include/asm/kvm_host.h | 6 +++---
 virt/kvm/arm/arm.c                | 8 ++++----
 3 files changed, 8 insertions(+), 8 deletions(-)
Christoffer Dall - Dec. 10, 2018, 10:13 a.m.
On Thu, Dec 06, 2018 at 05:31:20PM +0000, Marc Zyngier wrote:
> An SVE system is so far the only case where we mandate VHE. As we're
> starting to grow this requirements, let's slightly rework the way we
> deal with that situation, allowing for easy extension of this check.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>  arch/arm/include/asm/kvm_host.h   | 2 +-
>  arch/arm64/include/asm/kvm_host.h | 6 +++---
>  virt/kvm/arm/arm.c                | 8 ++++----
>  3 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 5ca5d9af0c26..2184d9ddb418 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -285,7 +285,7 @@ void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);
>  
>  struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
>  
> -static inline bool kvm_arch_check_sve_has_vhe(void) { return true; }
> +static inline bool kvm_arch_requires_vhe(void) { return false; }
>  static inline void kvm_arch_hardware_unsetup(void) {}
>  static inline void kvm_arch_sync_events(struct kvm *kvm) {}
>  static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 52fbc823ff8c..d6d9aa76a943 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -422,7 +422,7 @@ static inline void __cpu_init_hyp_mode(phys_addr_t pgd_ptr,
>  	}
>  }
>  
> -static inline bool kvm_arch_check_sve_has_vhe(void)
> +static inline bool kvm_arch_requires_vhe(void)
>  {
>  	/*
>  	 * The Arm architecture specifies that implementation of SVE
> @@ -430,9 +430,9 @@ static inline bool kvm_arch_check_sve_has_vhe(void)
>  	 * relies on this when SVE is present:
>  	 */
>  	if (system_supports_sve())
> -		return has_vhe();
> -	else
>  		return true;
> +
> +	return false;
>  }
>  
>  static inline void kvm_arch_hardware_unsetup(void) {}
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index 23774970c9df..1db4c15edcdd 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -1640,8 +1640,10 @@ int kvm_arch_init(void *opaque)
>  		return -ENODEV;
>  	}
>  
> -	if (!kvm_arch_check_sve_has_vhe()) {
> -		kvm_pr_unimpl("SVE system without VHE unsupported.  Broken cpu?");
> +	in_hyp_mode = is_kernel_in_hyp_mode();
> +
> +	if (!in_hyp_mode && kvm_arch_requires_vhe()) {
> +		kvm_pr_unimpl("CPU requiring VHE was booted in non-VHE mode");

nit: The error message feels weird to me (are we reporting CPU bugs?)
and I'm not sure about the unimpl and I think there's a linse space
missing.

How about:

	kvm_err("Cannot support this CPU in non-VHE mode, not initializing\n");

If we wanted to be super helpful, we could expand
kvm_arch_requires_vhe() with a print statement saying:
		
	kvm_err("SVE detected, requiring VHE mode\n");

But thay may be overkill.


>  		return -ENODEV;
>  	}
>  
> @@ -1657,8 +1659,6 @@ int kvm_arch_init(void *opaque)
>  	if (err)
>  		return err;
>  
> -	in_hyp_mode = is_kernel_in_hyp_mode();
> -
>  	if (!in_hyp_mode) {
>  		err = init_hyp_mode();
>  		if (err)
> -- 
> 2.19.2
> 

Otherwise:

Acked-by: Christoffer Dall <christoffer.dall@arm.com>
Marc Zyngier - Dec. 10, 2018, 10:28 a.m.
On 10/12/2018 10:13, Christoffer Dall wrote:
> On Thu, Dec 06, 2018 at 05:31:20PM +0000, Marc Zyngier wrote:
>> An SVE system is so far the only case where we mandate VHE. As we're
>> starting to grow this requirements, let's slightly rework the way we
>> deal with that situation, allowing for easy extension of this check.
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
>> ---
>>  arch/arm/include/asm/kvm_host.h   | 2 +-
>>  arch/arm64/include/asm/kvm_host.h | 6 +++---
>>  virt/kvm/arm/arm.c                | 8 ++++----
>>  3 files changed, 8 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
>> index 5ca5d9af0c26..2184d9ddb418 100644
>> --- a/arch/arm/include/asm/kvm_host.h
>> +++ b/arch/arm/include/asm/kvm_host.h
>> @@ -285,7 +285,7 @@ void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);
>>  
>>  struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
>>  
>> -static inline bool kvm_arch_check_sve_has_vhe(void) { return true; }
>> +static inline bool kvm_arch_requires_vhe(void) { return false; }
>>  static inline void kvm_arch_hardware_unsetup(void) {}
>>  static inline void kvm_arch_sync_events(struct kvm *kvm) {}
>>  static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 52fbc823ff8c..d6d9aa76a943 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -422,7 +422,7 @@ static inline void __cpu_init_hyp_mode(phys_addr_t pgd_ptr,
>>  	}
>>  }
>>  
>> -static inline bool kvm_arch_check_sve_has_vhe(void)
>> +static inline bool kvm_arch_requires_vhe(void)
>>  {
>>  	/*
>>  	 * The Arm architecture specifies that implementation of SVE
>> @@ -430,9 +430,9 @@ static inline bool kvm_arch_check_sve_has_vhe(void)
>>  	 * relies on this when SVE is present:
>>  	 */
>>  	if (system_supports_sve())
>> -		return has_vhe();
>> -	else
>>  		return true;
>> +
>> +	return false;
>>  }
>>  
>>  static inline void kvm_arch_hardware_unsetup(void) {}
>> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
>> index 23774970c9df..1db4c15edcdd 100644
>> --- a/virt/kvm/arm/arm.c
>> +++ b/virt/kvm/arm/arm.c
>> @@ -1640,8 +1640,10 @@ int kvm_arch_init(void *opaque)
>>  		return -ENODEV;
>>  	}
>>  
>> -	if (!kvm_arch_check_sve_has_vhe()) {
>> -		kvm_pr_unimpl("SVE system without VHE unsupported.  Broken cpu?");
>> +	in_hyp_mode = is_kernel_in_hyp_mode();
>> +
>> +	if (!in_hyp_mode && kvm_arch_requires_vhe()) {
>> +		kvm_pr_unimpl("CPU requiring VHE was booted in non-VHE mode");
> 
> nit: The error message feels weird to me (are we reporting CPU bugs?)
> and I'm not sure about the unimpl and I think there's a linse space
> missing.
> 
> How about:
> 
> 	kvm_err("Cannot support this CPU in non-VHE mode, not initializing\n");

Yup, works for me. Will, do you mind changing this message for me?

> 
> If we wanted to be super helpful, we could expand
> kvm_arch_requires_vhe() with a print statement saying:
> 		
> 	kvm_err("SVE detected, requiring VHE mode\n");
> 
> But thay may be overkill.

I started with that, but having kvm_pr*() in an include file has proved
to be challenging, so I decided to spend my time on something more
useful and quickly gave up... :-/

> 
> 
>>  		return -ENODEV;
>>  	}
>>  
>> @@ -1657,8 +1659,6 @@ int kvm_arch_init(void *opaque)
>>  	if (err)
>>  		return err;
>>  
>> -	in_hyp_mode = is_kernel_in_hyp_mode();
>> -
>>  	if (!in_hyp_mode) {
>>  		err = init_hyp_mode();
>>  		if (err)
>> -- 
>> 2.19.2
>>
> 
> Otherwise:
> 
> Acked-by: Christoffer Dall <christoffer.dall@arm.com>
> 

Thanks,

	M.
Will Deacon - Dec. 10, 2018, 12:40 p.m.
On Mon, Dec 10, 2018 at 10:28:05AM +0000, Marc Zyngier wrote:
> On 10/12/2018 10:13, Christoffer Dall wrote:
> > On Thu, Dec 06, 2018 at 05:31:20PM +0000, Marc Zyngier wrote:
> >> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> >> index 23774970c9df..1db4c15edcdd 100644
> >> --- a/virt/kvm/arm/arm.c
> >> +++ b/virt/kvm/arm/arm.c
> >> @@ -1640,8 +1640,10 @@ int kvm_arch_init(void *opaque)
> >>  		return -ENODEV;
> >>  	}
> >>  
> >> -	if (!kvm_arch_check_sve_has_vhe()) {
> >> -		kvm_pr_unimpl("SVE system without VHE unsupported.  Broken cpu?");
> >> +	in_hyp_mode = is_kernel_in_hyp_mode();
> >> +
> >> +	if (!in_hyp_mode && kvm_arch_requires_vhe()) {
> >> +		kvm_pr_unimpl("CPU requiring VHE was booted in non-VHE mode");
> > 
> > nit: The error message feels weird to me (are we reporting CPU bugs?)
> > and I'm not sure about the unimpl and I think there's a linse space
> > missing.
> > 
> > How about:
> > 
> > 	kvm_err("Cannot support this CPU in non-VHE mode, not initializing\n");
> 
> Yup, works for me. Will, do you mind changing this message for me?

I pushed out an updated branch here:

https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=kvm/cortex-a76-erratum-1165522

which should address all of Christoffer's comments and add his tags.

I plan to merge that into for-next/core later today.

Will

Patch

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 5ca5d9af0c26..2184d9ddb418 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -285,7 +285,7 @@  void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);
 
 struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
 
-static inline bool kvm_arch_check_sve_has_vhe(void) { return true; }
+static inline bool kvm_arch_requires_vhe(void) { return false; }
 static inline void kvm_arch_hardware_unsetup(void) {}
 static inline void kvm_arch_sync_events(struct kvm *kvm) {}
 static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 52fbc823ff8c..d6d9aa76a943 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -422,7 +422,7 @@  static inline void __cpu_init_hyp_mode(phys_addr_t pgd_ptr,
 	}
 }
 
-static inline bool kvm_arch_check_sve_has_vhe(void)
+static inline bool kvm_arch_requires_vhe(void)
 {
 	/*
 	 * The Arm architecture specifies that implementation of SVE
@@ -430,9 +430,9 @@  static inline bool kvm_arch_check_sve_has_vhe(void)
 	 * relies on this when SVE is present:
 	 */
 	if (system_supports_sve())
-		return has_vhe();
-	else
 		return true;
+
+	return false;
 }
 
 static inline void kvm_arch_hardware_unsetup(void) {}
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 23774970c9df..1db4c15edcdd 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -1640,8 +1640,10 @@  int kvm_arch_init(void *opaque)
 		return -ENODEV;
 	}
 
-	if (!kvm_arch_check_sve_has_vhe()) {
-		kvm_pr_unimpl("SVE system without VHE unsupported.  Broken cpu?");
+	in_hyp_mode = is_kernel_in_hyp_mode();
+
+	if (!in_hyp_mode && kvm_arch_requires_vhe()) {
+		kvm_pr_unimpl("CPU requiring VHE was booted in non-VHE mode");
 		return -ENODEV;
 	}
 
@@ -1657,8 +1659,6 @@  int kvm_arch_init(void *opaque)
 	if (err)
 		return err;
 
-	in_hyp_mode = is_kernel_in_hyp_mode();
-
 	if (!in_hyp_mode) {
 		err = init_hyp_mode();
 		if (err)