On Mon, Nov 11, 2019 at 03:50:07PM +0000, Jonathan Cameron wrote:
> > + cfg->l1ptr = dmam_alloc_coherent(smmu->dev, size,
> > + &cfg->l1ptr_dma,
> > + GFP_KERNEL | __GFP_ZERO);
>
> As before. Fairly sure __GFP_ZERO doesn't give you anything extra.
Indeed
> > + if (!cfg->l1ptr) {
> > + dev_warn(smmu->dev, "failed to allocate L1 context
> > table\n");
> > + return -ENOMEM;
> > + }
> > + }
> > +
> > + cfg->tables = devm_kzalloc(smmu->dev, sizeof(struct arm_smmu_cd_table) *
> > + cfg->num_tables, GFP_KERNEL);
> > + if (!cfg->tables) {
> > + ret = -ENOMEM;
> > + goto err_free_l1;
> > + }
> > +
> > + /* With two levels, leaf tables are allocated lazily */
> This comment is a kind of odd one. It is actually talking about what
> 'doesn't' happen here I think..
>
> Perhaps /*
> * Only allocate a leaf table for linear case.
> * With two levels, the leaf tables are allocated lazily.
> */
Yes, that's clearer
> > + if (!cfg->l1ptr) {
> > + ret = arm_smmu_alloc_cd_leaf_table(smmu, &cfg->tables[0],
> > + max_contexts);
> > + if (ret)
> > + goto err_free_tables;
> > + }
> > +
> > + return 0;
> > +
> > +err_free_tables:
> > + devm_kfree(smmu->dev, cfg->tables);
> > +err_free_l1:
> > + if (cfg->l1ptr)
> > + dmam_free_coherent(smmu->dev, size, cfg->l1ptr, cfg->l1ptr_dma);
>
> This cleanup only occurs if we have had an error.
> Is there potential for this to rerun at some point later? If so we should
> be careful to also reset relevant pointers - e.g. cfg->l1ptr = NULL as
> they are used to control the flow above.
Yes we should definitely clear l1ptr. The domain may be managed by a
device driver, and if attach_dev() fails they will call domain_free(),
which checks this pointer. Plus nothing prevents them from calling
attach_dev() again with the same domain.
> If there is no chance of a rerun why bother cleaning them up at all?
> Something
> has gone horribly wrong so let the eventual smmu cleanup deal with them.
The domain is much shorter-lived than the SMMU device, so we need this
cleanup.
> > + return ret;
> > }
> >
> > static void arm_smmu_free_cd_tables(struct arm_smmu_domain *smmu_domain)
> > {
> > + int i;
> > struct arm_smmu_device *smmu = smmu_domain->smmu;
> > struct arm_smmu_s1_cfg *cfg = &smmu_domain->s1_cfg;
> > + size_t num_leaf_entries = 1 << cfg->s1cdmax;
> > + struct arm_smmu_cd_table *table = cfg->tables;
> >
> > - arm_smmu_free_cd_leaf_table(smmu, &cfg->table, 1 << cfg->s1cdmax);
> > + if (cfg->l1ptr) {
> > + size_t size = cfg->num_tables * (CTXDESC_L1_DESC_DWORDS << 3);
> > +
> > + dmam_free_coherent(smmu->dev, size, cfg->l1ptr, cfg->l1ptr_dma);
>
> As above, if we can call this in a fashion that makes sense
> other than in eventual smmu tear down, then we need to be
> careful to reset the pointers. If not, then why are we
> clearing
> managed resourced by hand anyway?
Yes, we call this on the error cleanup path (not only domain_free()), so
it needs to leave the domain in a usable state.
Thanks,
Jean
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