> On Jun 1, 2021, at 10:27 AM, Robin Murphy <robin.mur...@arm.com> wrote: > > On 2021-06-01 17:39, Nadav Amit wrote: >>> On Jun 1, 2021, at 8:59 AM, Robin Murphy <robin.mur...@arm.com> wrote: >>> >>> On 2021-05-02 07:59, Nadav Amit wrote: >>>> From: Nadav Amit <na...@vmware.com> >>>> Some IOMMU architectures perform invalidations regardless of the page >>>> size. In such architectures there is no need to sync when the page size >>>> changes or to regard pgsize when making interim flush in >>>> iommu_iotlb_gather_add_page(). >>>> Add a "ignore_gather_pgsize" property for each IOMMU-ops to decide >>>> whether gather's pgsize is tracked and triggers a flush. >>> >>> I've objected before[1], and I'll readily object again ;) >>> >>> I still think it's very silly to add a bunch of indirection all over the >>> place to make a helper function not do the main thing it's intended to help >>> with. If you only need trivial address gathering then it's far simpler to >>> just implement trivial address gathering. I suppose if you really want to >>> you could factor out another helper to share the 5 lines of code which >>> ended up in mtk-iommu (see commit f21ae3b10084). >> Thanks, Robin. >> I read your comments but I cannot fully understand the alternative that you >> propose, although I do understand your objection to the indirection >> “ignore_gather_pgsize”. Would it be ok if “ignore_gather_pgsize" was >> provided as an argument for iommu_iotlb_gather_add_page()? > > No, I mean if iommu_iotlb_gather_add_page() doesn't have the behaviour your > driver wants, just don't call it. Write or factor out a suitable helper that > *does* do what you want and call that, or just implement the logic directly > inline. Indirect argument or not, it just doesn't make much sense to have a > helper function call which says "do this except don't do most of it". > >> In general, I can live without this patch. It probably would have negligent >> impact on performance anyhow. > > As I implied, it sounds like your needs are the same as the Mediatek driver > had, so you could readily factor out a new page-size-agnostic gather helper > from that. I fully support making the functional change to amd-iommu > *somehow* - nobody likes unnecessary syncs - just not with this particular > implementation :)
Hm… avoid code duplication I need to extract some common code to another
function.
Is the following resembles what you had in mind (untested)?
-- >8 --
Subject: [PATCH] iommu: add iommu_iotlb_gather_add_page_ignore_pgsize()
---
drivers/iommu/mtk_iommu.c | 7 ++---
include/linux/iommu.h | 55 ++++++++++++++++++++++++++++++---------
2 files changed, 44 insertions(+), 18 deletions(-)
diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
index e168a682806a..5890e745bed3 100644
--- a/drivers/iommu/mtk_iommu.c
+++ b/drivers/iommu/mtk_iommu.c
@@ -520,12 +520,9 @@ static size_t mtk_iommu_unmap(struct iommu_domain *domain,
struct iommu_iotlb_gather *gather)
{
struct mtk_iommu_domain *dom = to_mtk_domain(domain);
- unsigned long end = iova + size - 1;
- if (gather->start > iova)
- gather->start = iova;
- if (gather->end < end)
- gather->end = end;
+ iommu_iotlb_gather_update_range(gather, iova, size);
+
return dom->iop->unmap(dom->iop, iova, size, gather);
}
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 9ca6e6b8084d..037434b6eb4c 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -535,29 +535,58 @@ static inline void iommu_iotlb_sync(struct iommu_domain
*domain,
iommu_iotlb_gather_init(iotlb_gather);
}
-static inline void iommu_iotlb_gather_add_page(struct iommu_domain *domain,
+static inline
+void iommu_iotlb_gather_update_range(struct iommu_iotlb_gather *gather,
+ unsigned long iova, size_t size)
+{
+ unsigned long start = iova, end = start + size - 1;
+
+ if (gather->end < end)
+ gather->end = end;
+
+ if (gather->start > start)
+ gather->start = start;
+
+ gather->pgsize = size;
+}
+
+static inline
+bool iommu_iotlb_gather_is_disjoint(struct iommu_iotlb_gather *gather,
+ unsigned long iova, size_t size)
+{
+ return iova + size < gather->start || iova > gather->end + 1;
+}
+
+static inline
+void iommu_iotlb_gather_add_page_ignore_pgsize(struct iommu_domain *domain,
struct iommu_iotlb_gather
*gather,
unsigned long iova, size_t size)
{
- unsigned long start = iova, end = start + size - 1;
+ /*
+ * Only if the new page is disjoint from the current range, then sync
+ * the TLB so that the gather structure can be rewritten.
+ */
+ if (iommu_iotlb_gather_is_disjoint(gather, iova, size) &&
gather->pgsize)
+ iommu_iotlb_sync(domain, gather);
+
+ iommu_iotlb_gather_update_range(gather, iova, size);
+}
+static inline void iommu_iotlb_gather_add_page(struct iommu_domain *domain,
+ struct iommu_iotlb_gather
*gather,
+ unsigned long iova, size_t size)
+{
/*
* If the new page is disjoint from the current range or is mapped at
* a different granularity, then sync the TLB so that the gather
* structure can be rewritten.
*/
- if (gather->pgsize != size ||
- end + 1 < gather->start || start > gather->end + 1) {
- if (gather->pgsize)
- iommu_iotlb_sync(domain, gather);
- gather->pgsize = size;
- }
-
- if (gather->end < end)
- gather->end = end;
+ if ((gather->pgsize != size ||
+ iommu_iotlb_gather_is_disjoint(gather, iova, size)) &&
+ gather->pgsize)
+ iommu_iotlb_sync(domain, gather);
- if (gather->start > start)
- gather->start = start;
+ iommu_iotlb_gather_update_range(gather, iova, size);
}
/* PCI device grouping function */
--
2.25.1
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