Re: [PATCH 3/4] iommu: Introduce IOMMU call-back for processing struct KVM assigned to VFIO

From: "Suthikulpanit, Suravee" <suravee.suthikulpanit@amd.com>
To: Robin Murphy <robin.murphy@arm.com>,
	linux-kernel@vger.kernel.org, iommu@lists.linux.dev
Cc: joro@8bytes.org, ashish.kalra@amd.com, thomas.lendacky@amd.com,
	vasant.hegde@amd.com, jon.grimm@amd.com
Subject: Re: [PATCH 3/4] iommu: Introduce IOMMU call-back for processing struct KVM assigned to VFIO
Date: Tue, 17 Jan 2023 11:20:37 +0700	[thread overview]
Message-ID: <04dc1bc9-05ed-f6ed-f01f-7d28600fc0ce@amd.com> (raw)
In-Reply-To: <e4d5db37-a7b9-9b33-4ecf-c168b6d41a9a@arm.com>

Hi Robin,

On 1/10/2023 10:11 PM, Robin Murphy wrote:
> On 2023-01-10 14:31, Suravee Suthikulpanit wrote:
>> Currently, VFIO provide an kvm_vfio_file_set_kvm() interface for 
>> assigning
>> a KVM structure to a VFIO group. The information in struct KVM is also
>> useful for IOMMU drivers when setting up VFIO domain.
>>
>> Introduce struct iommu_domain_ops.set_kvm call-back function to allow
>> IOMMU drivers to provide call-back to process the struct KVM assigned.
> 
> Hmm, it sounds like this has quite some overlap of intent with the 
> existing "enable_nesting" op, and my gut feeling is that it's not great 
> to have two completely different "this is a VFIO domain" mechanisms... :/
> 
> Robin.

Actually, the intention is to communicate KVM information, which is 
already available to the VFIO down to the AMD IOMMU driver layer. I am 
not sure if the enable_nesting() has enough information or the same 
intention since that only communicates VFIO domain information.

Thanks,
Suravee