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

[Eric Auger]

Hi Nicolin,

On 3/13/26 1:36 AM, Nicolin Chen wrote:
> 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@xxxxxxxxxx>
> Reported-by: Shameer Kolothum <skolothumtho@xxxxxxxxxx>
> Closes: https://lore.kernel.org/qemu-devel/CH3PR12MB754836BEE54E39B30C7210C0AB44A@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
> Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>

Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>

Eric
> ---
>  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);
>  }
>