linux-kernel - Re: [PATCH] vfio-pci/zdev: require KVM to be built-in

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Date:   Tue, 16 Aug 2022 09:55:04 +0200
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.org
Cc:     kernel test robot <lkp@...el.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Eric Farman <farman@...ux.ibm.com>, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH] vfio-pci/zdev: require KVM to be built-in



On 8/16/22 08:04, Randy Dunlap wrote:
> Hi--
> 
> On 8/15/22 02:43, Pierre Morel wrote:
>> Thank you Randy for this good catch.
>> However forcing KVM to be include statically in the kernel when using VFIO_PCI extensions is not a good solution for us I think.
>>
>> I suggest we better do something like:
>>
>> ----
>>
>> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
>> index 6287a843e8bc..1733339cc4eb 100644
>> --- a/arch/s390/include/asm/kvm_host.h
>> +++ b/arch/s390/include/asm/kvm_host.h
>> @@ -1038,7 +1038,7 @@ static inline void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu) {}
>>   #define __KVM_HAVE_ARCH_VM_FREE
>>   void kvm_arch_free_vm(struct kvm *kvm);
>>
>> -#ifdef CONFIG_VFIO_PCI_ZDEV_KVM
>> +#if defined(CONFIG_VFIO_PCI_ZDEV_KVM) || defined(CONFIG_VFIO_PCI_ZDEV_KVM_MODULE)
> 
> This all looks good except for the line above.
> It should be:
> 
> #if IS_ENABLED(CONFIG_VFIO_PCI_ZDEV_KVM)
> 
> Thanks.

Yes, better, thanks.
How do we do? Should I repost it with reported-by you or do you want to 
post it?

Pierre


> 
> 
>>   int kvm_s390_pci_register_kvm(struct zpci_dev *zdev, struct kvm *kvm);
>>   void kvm_s390_pci_unregister_kvm(struct zpci_dev *zdev);
>>   #else
>> diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
>> index f9d0c908e738..bbc375b028ef 100644
>> --- a/drivers/vfio/pci/Kconfig
>> +++ b/drivers/vfio/pci/Kconfig
>> @@ -45,9 +45,9 @@ config VFIO_PCI_IGD
>>   endif
>>
>>   config VFIO_PCI_ZDEV_KVM
>> -       bool "VFIO PCI extensions for s390x KVM passthrough"
>> +       def_tristate y
>> +       prompt "VFIO PCI extensions for s390x KVM passthrough"
>>          depends on S390 && KVM
>> -       default y
>>          help
>>            Support s390x-specific extensions to enable support for enhancements
>>            to KVM passthrough capabilities, such as interpretive execution of
>>
>> ----
>>
>> What do you think? It seems to me it solves the problem, what do you think?
>>
>> Regards,
>> Pierre
> 
> 

-- 
Pierre Morel
IBM Lab Boeblingen