Re: [PATCH v7 12/14] iommu/arm-smmu-v3: Introduce struct arm_smmu_vmaster

Pranjal Shrivastava
2025-02-25T17:08:29Z

On Tue, Feb 25, 2025 at 08:41:27AM -0800, Nicolin Chen wrote:
> On Tue, Feb 25, 2025 at 12:02:25PM -0400, Jason Gunthorpe wrote:
> > On Mon, Feb 24, 2025 at 03:45:33PM -0800, Nicolin Chen wrote:
> >
> > > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
> > > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
> > > @@ -95,8 +95,6 @@ int arm_smmu_attach_prepare_vmaster(struct arm_smmu_attach_state *state,
> > >
> > > iommu_group_mutex_assert(state->master->dev);
> > >
> > > - if (domain->type != IOMMU_DOMAIN_NESTED)
> > > - return 0;
> > > nested_domain = to_smmu_nested_domain(domain);
> > >
> > > /* Skip invalid vSTE */
> > > @@ -122,19 +120,9 @@ void arm_smmu_attach_commit_vmaster(struct arm_smmu_attach_state *state)
> > > {
> > > struct arm_smmu_master *master = state->master;
> > >
> > > - mutex_lock(&master->smmu->streams_mutex);
> > > - if (state->vmaster != master->vmaster) {
> > > - kfree(master->vmaster);
> > > - master->vmaster = state->vmaster;
> > > - }
> > > - mutex_unlock(&master->smmu->streams_mutex);
> > > -}
> > > -
> > > -void arm_smmu_master_clear_vmaster(struct arm_smmu_master *master)
> > > -{
> > > mutex_lock(&master->smmu->streams_mutex);
> > > kfree(master->vmaster);
> > > - master->vmaster = NULL;
> > > + master->vmaster = state->vmaster;
> > > mutex_unlock(&master->smmu->streams_mutex);
> > > }
> >
> > I'd leave the clear_vmaster just for clarity. Commit should not be
> > unpaired with prepare in the other functions.
> >
> > It looks fine with this on top too
> >
> > Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
>
> Ack. I added it back and a #ifdef to the vmaster:
>
> +void arm_smmu_master_clear_vmaster(struct arm_smmu_master *master)
> +{
> + struct arm_smmu_attach_state state = { .master = master };
> +
> + arm_smmu_attach_commit_vmaster(&state);
> +}
> [...]
> @@ -824,6 +829,9 @@ struct arm_smmu_master {
> struct arm_smmu_device *smmu;
> struct device *dev;
> struct arm_smmu_stream *streams;
> +#ifdef CONFIG_ARM_SMMU_V3_IOMMUFD
> + struct arm_smmu_vmaster *vmaster; /* use smmu->streams_mutex */
> +#endif
> /* Locked by the iommu core using the group mutex */
> struct arm_smmu_ctx_desc_cfg cd_table;
> unsigned int num_streams;
> @@ -972,6 +980,9 @@ struct arm_smmu_attach_state {
> bool disable_ats;
> ioasid_t ssid;
> /* Resulting state */
> +#ifdef CONFIG_ARM_SMMU_V3_IOMMUFD
> + struct arm_smmu_vmaster *vmaster;
> +#endif
> bool ats_enabled;
> };
>

Umm.. I'm not too sure how I feel about these #ifdefs _between_ a struct
definition. Given that currently, the arm_smmu_v3.h file doesn't have
such `#ifdef CONFIG`s between structs. I'd say, in case
CONFIG_ARM_SMMU_V3_IOMMUFD is turned off, we can simply leave the
vmaster ptr NULL?

-Praan