Re: [PART1 V5 13/13] svm: Manage vcpu load/unload when enable AVIC

[Paolo Bonzini]

On 10/05/2016 17:43, Paolo Bonzini wrote:
> 
> 
> On 04/05/2016 21:09, Suravee Suthikulpanit wrote:
>> From: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
>>
>> When a vcpu is loaded/unloaded to a physical core, we need to update
>> host physical APIC ID information in the Physical APIC-ID table
>> accordingly.
>>
>> Also, when vCPU is blocking/un-blocking (due to halt instruction),
>> we need to make sure that the is-running bit in set accordingly in the
>> physical APIC-ID table.
>>
>> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
>> Reviewed-by: Radim KrÄmÃÅ <rkrcmar@xxxxxxxxxx>
>> ---
> 
> I think this is the only patch that needs a little more work, because 
> there are a bunch of unused return values that really should be 
> WARN_ON.  In addition the load and put cases are different enough that 
> they should be separate functions.
> 
> Can you please test this?
> 
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index f3dbf1d33a61..3168d6c8d24f 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -184,7 +184,7 @@ struct vcpu_svm {
>  	u32 ldr_reg;
>  	struct page *avic_backing_page;
>  	u64 *avic_physical_id_cache;
> -	bool avic_is_blocking;
> +	bool avic_is_running;
>  };
>  
>  #define AVIC_LOGICAL_ID_ENTRY_GUEST_PHYSICAL_ID_MASK	(0xFF)
> @@ -1321,18 +1321,20 @@ free_avic:
>  /**
>   * This function is called during VCPU halt/unhalt.
>   */
> -static int avic_set_running(struct kvm_vcpu *vcpu, bool is_run)
> +static void avic_set_running(struct kvm_vcpu *vcpu, bool is_run)
>  {
>  	u64 entry;
>  	int h_physical_id = __default_cpu_present_to_apicid(vcpu->cpu);
>  	struct vcpu_svm *svm = to_svm(vcpu);
>  
>  	if (!kvm_vcpu_apicv_active(vcpu))
> -		return 0;
> +		return;
> +
> +	svm->avic_is_running = is_run;
>  
>  	/* ID = 0xff (broadcast), ID > 0xff (reserved) */
> -	if (h_physical_id >= AVIC_MAX_PHYSICAL_ID_COUNT)
> -		return -EINVAL;
> +	if (WARN_ON(h_physical_id >= AVIC_MAX_PHYSICAL_ID_COUNT))
> +		return;
>  
>  	entry = READ_ONCE(*(svm->avic_physical_id_cache));
>  	WARN_ON(is_run == !!(entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK));
> @@ -1341,36 +1343,45 @@ static int avic_set_running(struct kvm_vcpu *vcpu, bool is_run)
>  	if (is_run)
>  		entry |= AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;
>  	WRITE_ONCE(*(svm->avic_physical_id_cache), entry);
> -
> -	return 0;
>  }
>  
> -static int avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu, bool is_load)
> +static void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>  {
>  	u64 entry;
> +	/* ID = 0xff (broadcast), ID > 0xff (reserved) */
>  	int h_physical_id = __default_cpu_present_to_apicid(cpu);
>  	struct vcpu_svm *svm = to_svm(vcpu);
>  
>  	if (!kvm_vcpu_apicv_active(vcpu))
> -		return 0;
> +		return;
>  
> -	/* ID = 0xff (broadcast), ID > 0xff (reserved) */
> -	if (h_physical_id >= AVIC_MAX_PHYSICAL_ID_COUNT)
> -		return -EINVAL;
> +	if (WARN_ON(h_physical_id >= AVIC_MAX_PHYSICAL_ID_COUNT))
> +		return;
>  
>  	entry = READ_ONCE(*(svm->avic_physical_id_cache));
> -	WARN_ON(is_load && (entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK));
> +	WARN_ON(entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK);
> +
> +	entry &= ~AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK;
> +	entry |= (h_physical_id & AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK);
>  
>  	entry &= ~AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;
> -	if (is_load) {
> -		entry &= ~AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK;
> -		entry |= (h_physical_id & AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK);
> -		if (!svm->avic_is_blocking)
> -			entry |= AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;
> -	}
> +	if (svm->avic_is_running)
> +		entry |= AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;
> +
>  	WRITE_ONCE(*(svm->avic_physical_id_cache), entry);
> +}
>  
> -	return 0;
> +static void avic_vcpu_put(struct kvm_vcpu *vcpu)
> +{
> +	u64 entry;
> +	struct vcpu_svm *svm = to_svm(vcpu);
> +
> +	if (!kvm_vcpu_apicv_active(vcpu))
> +		return;
> +
> +	entry = READ_ONCE(*(svm->avic_physical_id_cache));
> +	entry &= ~AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;
> +	WRITE_ONCE(*(svm->avic_physical_id_cache), entry);
>  }
>  
>  static void svm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
> @@ -1436,10 +1447,10 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
>  			goto free_page4;
>  	}
>  
> -	/* We initialize this flag to one to make sure that the is_running
> +	/* We initialize this flag to true to make sure that the is_running
>  	 * bit would be set the first time the vcpu is loaded.
>  	 */
> -	svm->avic_is_blocking = false;
> +	svm->avic_is_running = true;
>  
>  	svm->nested.hsave = page_address(hsave_page);
>  
> @@ -1518,7 +1529,7 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>  	if (static_cpu_has(X86_FEATURE_RDTSCP))
>  		wrmsrl(MSR_TSC_AUX, svm->tsc_aux);
>  
> -	avic_vcpu_load(vcpu, cpu, true);
> +	avic_vcpu_load(vcpu, cpu);
>  }
>  
>  static void svm_vcpu_put(struct kvm_vcpu *vcpu)
> @@ -1526,7 +1537,7 @@ static void svm_vcpu_put(struct kvm_vcpu *vcpu)
>  	struct vcpu_svm *svm = to_svm(vcpu);
>  	int i;
>  
> -	avic_vcpu_load(vcpu, 0, false);
> +	avic_vcpu_put(vcpu);
>  
>  	++vcpu->stat.host_state_reload;
>  	kvm_load_ldt(svm->host.ldt);
> @@ -1545,13 +1556,11 @@ static void svm_vcpu_put(struct kvm_vcpu *vcpu)
>  
>  static void svm_vcpu_blocking(struct kvm_vcpu *vcpu)
>  {
> -	to_svm(vcpu)->avic_is_blocking = true;
>  	avic_set_running(vcpu, false);
>  }
>  
>  static void svm_vcpu_unblocking(struct kvm_vcpu *vcpu)
>  {
> -	to_svm(vcpu)->avic_is_blocking = false;
>  	avic_set_running(vcpu, true);
>  }
>  
> 
> The two functions now have the same signature as their callers,
> svm_vcpu_load and svm_vcpu_put.

Radim, does this look sane?  I plan to include it in my pull request
(I'm running AMD autotest now and it passed the first few tests).

Thanks,

Paolo