[PATCH 1/2] iommu/tegra241-cmdqv: Set supports_cmd op in tegra241_vcmdq_hw_init()

[Shameer Kolothum Thodi]

> -----Original Message-----
> From: Nicolin Chen <nicolinc at nvidia.com>
> Sent: 13 March 2026 00:37
> To: will at kernel.org; robin.murphy at arm.com; Jason Gunthorpe
> <jgg at nvidia.com>; kevin.tian at intel.com
> Cc: joro at 8bytes.org; linux-tegra at vger.kernel.org; linux-arm-
> kernel at lists.infradead.org; iommu at lists.linux.dev; linux-
> kernel at vger.kernel.org; eric.auger at redhat.com; Shameer Kolothum Thodi
> <skolothumtho at nvidia.com>
> Subject: [PATCH 1/2] iommu/tegra241-cmdqv: Set supports_cmd op in
> tegra241_vcmdq_hw_init()
> 
> vintf->hyp_own is finalized in tegra241_vintf_hw_init(). On the other hand,
> tegra241_vcmdq_alloc_smmu_cmdq() is called via an init_structures callback,
> which is earlier than tegra241_vintf_hw_init().
> 
> This results in the supports_cmd op always being set to the guest function,
> although this doesn't break any functionality nor have some noticeable perf
> impact since non-invalidation commands are not issued in the perf sensitive
> context.
> 
> Fix this by moving supports_cmd to tegra241_vcmdq_hw_init().
> 
> After this change,
>  - For a guest kernel, this will be a status quo
>  - For a host kernel, non-invalidation commands will be issued to VCMDQ(s)
> 
> Fixes: a9d40285bdef ("iommu/tegra241-cmdqv: Limit CMDs for VCMDQs of a
> guest owned VINTF")
> Reported-by: Eric Auger <eric.auger at redhat.com>
> Reported-by: Shameer Kolothum <skolothumtho at nvidia.com>
> Closes: https://lore.kernel.org/qemu-
> devel/CH3PR12MB754836BEE54E39B30C7210C0AB44A at CH3PR12MB7548
> .namprd12.prod.outlook.com/
> Signed-off-by: Nicolin Chen <nicolinc at nvidia.com>
> ---

Ran few tests with QEMU toggling HYP_OWN bit, and this now enforces
that QEMU sets HYP_OWN for VCMDQ to work properly.

Tested-by: Shameer Kolothum <skolothumtho at nvidia.com>

Thanks,
Shameer

>  drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
> b/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
> index 6fe5563eaf9eb..83f6e9f6c51d6 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
> @@ -479,6 +479,10 @@ static int tegra241_vcmdq_hw_init(struct
> tegra241_vcmdq *vcmdq)
>  	/* Reset VCMDQ */
>  	tegra241_vcmdq_hw_deinit(vcmdq);
> 
> +	/* vintf->hyp_own is a HW state finalized in tegra241_vintf_hw_init()
> */
> +	if (!vcmdq->vintf->hyp_own)
> +		vcmdq->cmdq.supports_cmd =
> tegra241_guest_vcmdq_supports_cmd;
> +
>  	/* Configure and enable VCMDQ */
>  	writeq_relaxed(vcmdq->cmdq.q.q_base,
> REG_VCMDQ_PAGE1(vcmdq, BASE));
> 
> @@ -639,9 +643,6 @@ static int tegra241_vcmdq_alloc_smmu_cmdq(struct
> tegra241_vcmdq *vcmdq)
>  	q->q_base = q->base_dma & VCMDQ_ADDR;
>  	q->q_base |= FIELD_PREP(VCMDQ_LOG2SIZE, q->llq.max_n_shift);
> 
> -	if (!vcmdq->vintf->hyp_own)
> -		cmdq->supports_cmd =
> tegra241_guest_vcmdq_supports_cmd;
> -
>  	return arm_smmu_cmdq_init(smmu, cmdq);
>  }
> 
> --
> 2.43.0