linux-kernel - Re: [PATCH 6/6] KVM: SEV-ES: reuse advance_sev_es_emulated

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Date:   Wed, 15 Jun 2022 16:41:24 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH 6/6] KVM: SEV-ES: reuse advance_sev_es_emulated_ins for
 OUT too

On 6/10/22 00:50, Sean Christopherson wrote:
> On Wed, Jun 08, 2022, Paolo Bonzini wrote:
>> complete_emulator_pio_in only has to be called by
>> complete_sev_es_emulated_ins now; therefore, all that the function does
>> now is adjust sev_pio_count and sev_pio_data.  Which is the same for
>> both IN and OUT.
>>
>> No functional change intended.
>>
>> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
>> ---
>>   arch/x86/kvm/x86.c | 19 +++++++++----------
>>   1 file changed, 9 insertions(+), 10 deletions(-)
>>
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index fd4382602f65..a3651aa74ed7 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -13007,6 +13007,12 @@ int kvm_sev_es_mmio_read(struct kvm_vcpu *vcpu, gpa_t gpa, unsigned int bytes,
>>   }
>>   EXPORT_SYMBOL_GPL(kvm_sev_es_mmio_read);
>>   
>> +static void advance_sev_es_emulated_pio(struct kvm_vcpu *vcpu, unsigned count, int size)
>> +{
>> +	vcpu->arch.sev_pio_count -= count;
>> +	vcpu->arch.sev_pio_data += count * size;
>> +}
>> +
>>   static int kvm_sev_es_outs(struct kvm_vcpu *vcpu, unsigned int size,
>>   			   unsigned int port);
>>   
>> @@ -13030,8 +13036,7 @@ static int kvm_sev_es_outs(struct kvm_vcpu *vcpu, unsigned int size,
>>   		int ret = emulator_pio_out(vcpu, size, port, vcpu->arch.sev_pio_data, count);
>>   
>>   		/* memcpy done already by emulator_pio_out.  */
>> -		vcpu->arch.sev_pio_count -= count;
>> -		vcpu->arch.sev_pio_data += count * vcpu->arch.pio.size;
>> +		advance_sev_es_emulated_pio(vcpu, count, size);
> 
> I think this is a bug fix that should go in a separate patch.  size == vcpu->arch.pio.size
> when kvm_sev_es_outs() is called from complete_sev_es_emulated_outs(), but when
> it's called from kvm_sev_es_string_io() it will hold the size of the previous PIO.

It's not a bugfix for current master, because emulator_pio_out() sets 
vcpu->arch.pio.size = size.

However, it has to be moved before "KVM: x86: wean in-kernel PIO from 
vcpu->arch.pio*" or squashed therein.

Paolo

>>   		if (!ret)
>>   			break;
>>   
>> @@ -13047,12 +13052,6 @@ static int kvm_sev_es_outs(struct kvm_vcpu *vcpu, unsigned int size,
>>   static int kvm_sev_es_ins(struct kvm_vcpu *vcpu, unsigned int size,
>>   			  unsigned int port);
>>   
>> -static void advance_sev_es_emulated_ins(struct kvm_vcpu *vcpu, unsigned count, int size)
>> -{
>> -	vcpu->arch.sev_pio_count -= count;
>> -	vcpu->arch.sev_pio_data += count * size;
>> -}
>> -
>>   static int complete_sev_es_emulated_ins(struct kvm_vcpu *vcpu)
>>   {
>>   	unsigned count = vcpu->arch.pio.count;
>> @@ -13060,7 +13059,7 @@ static int complete_sev_es_emulated_ins(struct kvm_vcpu *vcpu)
>>   	int port = vcpu->arch.pio.port;
>>   
>>   	complete_emulator_pio_in(vcpu, vcpu->arch.sev_pio_data);
>> -	advance_sev_es_emulated_ins(vcpu, count, size);
>> +	advance_sev_es_emulated_pio(vcpu, count, size);
>>   	if (vcpu->arch.sev_pio_count)
>>   		return kvm_sev_es_ins(vcpu, size, port);
>>   	return 1;
>> @@ -13076,7 +13075,7 @@ static int kvm_sev_es_ins(struct kvm_vcpu *vcpu, unsigned int size,
>>   			break;
>>   
>>   		/* Emulation done by the kernel.  */
>> -		advance_sev_es_emulated_ins(vcpu, count, size);
>> +		advance_sev_es_emulated_pio(vcpu, count, size);
>>   		if (!vcpu->arch.sev_pio_count)
>>   			return 1;
>>   	}
>> -- 
>> 2.31.1
>>
>