linux-kernel - Re: [PATCH v5 3/7] iommu/arm-smmu-v3: Introduce a per-domain arm_smmu

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Message-ID: <aSXXQUevF41ATX8g@Asurada-Nvidia>
Date: Tue, 25 Nov 2025 08:20:17 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: Jason Gunthorpe <jgg@...dia.com>
CC: Will Deacon <will@...nel.org>, <jean-philippe@...aro.org>,
	<robin.murphy@....com>, <joro@...tes.org>, <balbirs@...dia.com>,
	<miko.lenczewski@....com>, <peterz@...radead.org>, <kevin.tian@...el.com>,
	<praan@...gle.com>, <linux-arm-kernel@...ts.infradead.org>,
	<iommu@...ts.linux.dev>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 3/7] iommu/arm-smmu-v3: Introduce a per-domain
 arm_smmu_invs array

On Tue, Nov 25, 2025 at 09:43:21AM -0400, Jason Gunthorpe wrote:
> On Mon, Nov 24, 2025 at 08:14:39PM -0800, Nicolin Chen wrote:
> > On Mon, Nov 24, 2025 at 09:42:31PM +0000, Will Deacon wrote:
> > > On Sat, Nov 08, 2025 at 12:08:04AM -0800, Nicolin Chen wrote:
> > > > +VISIBLE_IF_KUNIT
> > > > +struct arm_smmu_invs *arm_smmu_invs_merge(struct arm_smmu_invs *invs,
> > > > +					  struct arm_smmu_invs *to_merge)
> > > > +{
> > > > +	struct arm_smmu_invs *new_invs;
> > > > +	struct arm_smmu_inv *new;
> > > > +	size_t num_trashes = 0;
> > > > +	size_t num_adds = 0;
> > > > +	size_t i, j;
> > > > +
> > > > +	for (i = j = 0; i < invs->num_invs || j < to_merge->num_invs;) {
> > > 
> > > Maybe worth having a simple iterator macro for this?
> > 
> > I added two macros:
> > 
> > +#define arm_smmu_invs_for_each_inv(invs, idx, inv)              \
> > +	for (idx = 0, inv = &invs->inv[0]; idx < invs->num_invs; \
> > +	     inv = &invs->inv[++idx])
> > +#define arm_smmu_invs_for_each_idx_dual(invs1, idx1, invs2, idx2) \
> > +	for (idx1 = idx2 = 0; idx1 < invs1->num_invs || idx2 < invs2->num_invs;)
> 
> I think pull more stuff in. Something like this:
> 
> static inline struct arm_smmu_inv *
> arm_smmu_invs_iter_next(struct arm_smmu_invs *invs, size_t next,
> 			size_t *idx)
> {
> 	while (true) {
> 		if (next >= invs->num_invs) {
> 			*idx = next;
> 			return NULL;
> 		}
> 		if (!refcount_read(&invs->inv[next].users)) {
> 			next++;
> 			continue;
> 		}
> 		*idx = next;
> 		return &invs->inv[next];
> 	}
> }
> 
> static int arm_smmu_inv_cmp(const struct arm_smmu_inv *l,
> 			    const struct arm_smmu_inv *r)
> {
> 	if (l->smmu != r->smmu)
> 		return cmp_int((uintptr_t)l->smmu, (uintptr_t)r->smmu);
> 	if (l->type != r->type)
> 		return cmp_int(l->type, r->type);
> 	return cmp_int(l->id, r->id);
> }
> 
> static inline int arm_smmu_invs_iter_next_cmp(struct arm_smmu_invs *invs_lhs,
> 					      size_t next_lhs, size_t *idx_lhs,
> 					      struct arm_smmu_invs *invs_rhs,
> 					      size_t next_rhs, size_t *idx_rhs)
> {
> 	struct arm_smmu_inv *cur_lhs =
> 		arm_smmu_invs_iter_next(invs_lhs, 0, idx_lhs);
> 
> 	/*
> 	 * Compare of two sorted arrays items. If one side is past the end of
> 	 * the array, return the other side to let it run out the iteration.
> 	 */
> 	if (!cur_lhs)
> 		return -1;
> 	if (next_rhs >= invs_rhs->num_invs)
> 		return 1;
> 	return arm_smmu_inv_cmp(cur_lhs, &invs_rhs->inv[next_rhs]);
> }
> 
> /*
>  * Iterates over all non-trash entries in invs. idx is a stack variable
>  * to store the index, cur is a stack variable of 'struct arm_smmu_inv *'
>  */
> #define arm_smmu_invs_for_each_inv(invs, idx, cur)              \
> 	for (cur = arm_smmu_invs_iter_next(invs, 0, &(idx)); cur; \
> 	     cur = arm_smmu_invs_iter_next(invs, idx + 1, &(idx)))
> 
> /*
>  * Iterate over two sorted arrays computing a merge sort
>  */
> #define arm_smmu_invs_for_each_merge(invs_lhs, idx_lhs, invs_rhs, idx_rhs, \
> 				     cmp)                                  \
> 	for (cmp = arm_smmu_invs_iter_next_cmp(invs_lhs, 0, &(idx_lhs),    \
> 					       invs_rhs, 0, &(idx_rhs));   \
> 	     idx_lhs < invs_lhs->num_invs || idx_rhs < invs_rhs->num_invs; \
> 	     cmp = arm_smmu_invs_iter_next_cmp(                            \
> 		     invs_lhs, idx_lhs + (cmp <= 0 ? 1 : 0), &(idx_lhs),   \
> 		     invs_rhs, idx_rhs + (cmp >= 0 ? 1 : 0), &(idx_rhs)))
> 
> 
> 
> And then change the loops computing num_trash to work directly on actual things ignoring trash:
> 
> 	arm_smmu_invs_for_each_merge(invs, i, to_merge, j, cmp)
> 		new_size++;
> 	new_invs = arm_smmu_invs_alloc(new_size);

Cool. I will integrate this and send v6 today. Thanks for the help!

> Name should probably be for_each_.... though

Hmm, I thought it's more common to see structname_for_each_item,
such as list_for_each_item and xa_for_each?

Thanks
Nicolin