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From: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-coco@lists.linux.dev, kvmarm@lists.linux.dev,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, aik@amd.com,
	lukas@wunner.de, Samuel Ortiz <sameo@rivosinc.com>,
	Xu Yilun <yilun.xu@linux.intel.com>,
	Suzuki K Poulose <Suzuki.Poulose@arm.com>,
	Steven Price <steven.price@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>,
	Oliver Upton <oliver.upton@linux.dev>
Subject: Re: [RFC PATCH v1 07/38] iommufd/viommu: Add support to associate
 viommu with kvm instance
In-Reply-To: <20250728141026.GB26511@ziepe.ca>
References: <20250728135216.48084-1-aneesh.kumar@kernel.org>
 <20250728135216.48084-8-aneesh.kumar@kernel.org>
 <20250728141026.GB26511@ziepe.ca>
Date: Tue, 29 Jul 2025 14:00:22 +0530
Message-ID: <yq5azfcn9z6p.fsf@kernel.org>
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Jason Gunthorpe <jgg@ziepe.ca> 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 =3D -EBADF;
>> +	struct file *filp;
>> +
>> +	filp =3D fget(kvm_vm_fd);
>> +
>> +	if (!file_is_kvm(filp))
>> +		goto err_out;
>> +
>> +	/* hold the kvm reference via file descriptor */
>> +	viommu->kvm_filp =3D filp;
>> +	return 0;
>> +err_out:
>> +	viommu->kvm_filp =3D NULL;
>> +	fput(filp);
>> +	return rc;
>> +}
>> +
>> +static void viommu_put_kvm(struct iommufd_viommu *viommu)
>> +{
>> +	fput(viommu->kvm_filp);
>> +	viommu->kvm_filp =3D 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=E2=80=99ll update the patch with the sugg=
ested changes.

-aneesh