Re: [PATCH v1 00/16] iommufd: Add vIOMMU infrastructure (Part-4 vCMDQ)

Vasant Hegde
2025-04-24T11:22:06Z

On 4/23/2025 1:15 PM, Nicolin Chen wrote:
> On Wed, Apr 23, 2025 at 12:58:19PM +0530, Vasant Hegde wrote:
>> On 4/11/2025 12:07 PM, Nicolin Chen wrote:
>>> The vIOMMU object is designed to represent a slice of an IOMMU HW for its
>>> virtualization features shared with or passed to user space (a VM mostly)
>>> in a way of HW acceleration. This extended the HWPT-based design for more
>>> advanced virtualization feature.
>>>
>>> A vCMDQ introduced by this series as a part of the vIOMMU infrastructure
>>> represents a HW supported queue/buffer for VM to use exclusively, e.g.
>>> - NVIDIA's virtual command queue
>>> - AMD vIOMMU's command buffer
>>
>> I assume we can pass multiple buffer details (like GPA, size) from guest to
>> hypervisor. Is that correct understanding?
>
> Yes. The NVIDIA model passes through a Virtual-Interface to a VM,
> and the VM can allocate and map multiple command queues (buffers)
> to the V-Interface, by providing each command queue info in:
>
> +struct iommu_vcmdq_tegra241_cmdqv {
> + __u32 vcmdq_id;
> + __u32 vcmdq_log2size; // size
> + __aligned_u64 vcmdq_base; // GPA
> };

Nice. Thanks for the details.

-Vasant