Re: [RFC PATCH v1 07/38] iommufd/viommu: Add support to associate viommu with kvm instance

[Aneesh Kumar K . V]

Jason Gunthorpe <jgg@xxxxxxxx> writes:

> On Mon, Jul 28, 2025 at 07:21:44PM +0530, Aneesh Kumar K.V (Arm) wrote:
>
>> +#if IS_ENABLED(CONFIG_KVM)
>> +#include <linux/kvm_host.h>
>> +
>> +static int viommu_get_kvm(struct iommufd_viommu *viommu, int kvm_vm_fd)
>> +{
>> +	int rc = -EBADF;
>> +	struct file *filp;
>> +
>> +	filp = fget(kvm_vm_fd);
>> +
>> +	if (!file_is_kvm(filp))
>> +		goto err_out;
>> +
>> +	/* hold the kvm reference via file descriptor */
>> +	viommu->kvm_filp = filp;
>> +	return 0;
>> +err_out:
>> +	viommu->kvm_filp = NULL;
>> +	fput(filp);
>> +	return rc;
>> +}
>> +
>> +static void viommu_put_kvm(struct iommufd_viommu *viommu)
>> +{
>> +	fput(viommu->kvm_filp);
>> +	viommu->kvm_filp = NULL;
>> +}
>> +#endif
>
> Missing stub functions for !CONFIG_KVM?
>
> Looks like an OK design otherwise
>
>> @@ -1057,6 +1068,7 @@ struct iommu_viommu_alloc {
>>  	__u32 data_len;
>>  	__u32 __reserved;
>>  	__aligned_u64 data_uptr;
>> +	__u32 kvm_vm_fd;
>
> fds are __s32, they are signed numbers.
>

Thanks for the review comments. I’ll update the patch with the suggested changes.

-aneesh