linux-kernel - [PATCH 3/4] iommu/amd: Do not sync on page size changes

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Date:   Sat,  1 May 2021 23:59:59 -0700
From:   Nadav Amit <nadav.amit@...il.com>
To:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>
Cc:     Nadav Amit <namit@...are.com>, Jiajun Cao <caojiajun@...are.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: [PATCH 3/4] iommu/amd: Do not sync on page size changes

From: Nadav Amit <namit@...are.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.

Cc: Joerg Roedel <joro@...tes.org>
Cc: Will Deacon <will@...nel.org>
Cc: Jiajun Cao <caojiajun@...are.com>
Cc: iommu@...ts.linux-foundation.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Nadav Amit <namit@...are.com>
---
 drivers/iommu/amd/iommu.c | 1 +
 include/linux/iommu.h     | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index b8cabbbeed71..1849b53f2149 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -2215,6 +2215,7 @@ const struct iommu_ops amd_iommu_ops = {
 	.put_resv_regions = generic_iommu_put_resv_regions,
 	.is_attach_deferred = amd_iommu_is_attach_deferred,
 	.pgsize_bitmap	= AMD_IOMMU_PGSIZES,
+	.ignore_gather_pgsize = true,
 	.flush_iotlb_all = amd_iommu_flush_iotlb_all,
 	.iotlb_sync = amd_iommu_iotlb_sync,
 	.def_domain_type = amd_iommu_def_domain_type,
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 32d448050bf7..1fb2695418e9 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -284,6 +284,7 @@ struct iommu_ops {
 	int (*def_domain_type)(struct device *dev);
 
 	unsigned long pgsize_bitmap;
+	bool ignore_gather_pgsize;
 	struct module *owner;
 };
 
@@ -508,7 +509,7 @@ static inline void iommu_iotlb_gather_add_page(struct iommu_domain *domain,
 	 * a different granularity, then sync the TLB so that the gather
 	 * structure can be rewritten.
 	 */
-	if (gather->pgsize != size ||
+	if ((gather->pgsize != size && !domain->ops->ignore_gather_pgsize) ||
 	    end + 1 < gather->start || start > gather->end + 1) {
 		if (gather->pgsize)
 			iommu_iotlb_sync(domain, gather);
-- 
2.25.1