Re: [PATCH v8 12/14] iommu/arm-smmu-v3: Introduce struct arm_smmu_vmaster

Zhangfei Gao
2025-04-07T12:09:10Z

Hi, Nico

On Wed, 26 Feb 2025 at 01:35, Nicolin Chen <nicolinc@nvidia.com> wrote:
>
> Use it to store all vSMMU-related data. The vsid (Virtual Stream ID) will
> be the first use case. Since the vsid reader will be the eventq handler
> that already holds a streams_mutex, reuse that to fenche the vmaster too.
>
> Also add a pair of arm_smmu_attach_prepare/commit_vmaster helpers to set
> or unset the master->vmaster point. Put these helpers inside the existing
> arm_smmu_attach_prepare/commit().
>
> For identity/blocked ops that don't call arm_smmu_attach_prepare/commit(),
> add a simpler arm_smmu_master_clear_vmaster helper to unset the vmaster.
>
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Reviewed-by: Pranjal Shrivastavat <praan@google.com>
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
> ---

>
> +int arm_smmu_attach_prepare_vmaster(struct arm_smmu_attach_state *state,
> + struct arm_smmu_nested_domain *nested_domain)
> +{
> + struct arm_smmu_vmaster *vmaster;
> + unsigned long vsid;
> + int ret;
> +
> + iommu_group_mutex_assert(state->master->dev);
> +
> + /* Skip invalid vSTE */
> + if (!(nested_domain->ste[0] & cpu_to_le64(STRTAB_STE_0_V)))
> + return 0;

Why this is removed in v9 and 6.15-rc1?

I tested 6.15-rc1 the qemu failed to boot with qemu branch:
for_iommufd_veventq-v8
"failed to attach the bypass pagetable"

After adding this "skip check" back, the qemu works again.

Do we need to add this back?

Thanks