linux-kernel - [PATCH 5.12 492/677] iommu: Fix a boundary issue to avoid performance drop

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Message-Id: <20210512144853.731535713@linuxfoundation.org>
Date:   Wed, 12 May 2021 16:48:58 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Xiang Chen <chenxiang66@...ilicon.com>,
        Will Deacon <will@...nel.org>, Joerg Roedel <jroedel@...e.de>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.12 492/677] iommu: Fix a boundary issue to avoid performance drop

From: Xiang Chen <chenxiang66@...ilicon.com>

[ Upstream commit 3431c3f660a39f6ced954548a59dba6541ce3eb1 ]

After the change of patch ("iommu: Switch gather->end to the
inclusive end"), the performace drops from 1600+K IOPS to 1200K in our
kunpeng ARM64 platform.
We find that the range [start1, end1) actually is joint from the range
[end1, end2), but it is considered as disjoint after the change,
so it needs more times of TLB sync, and spends more time on it.
So fix the boundary issue to avoid performance drop.

Fixes: 862c3715de8f ("iommu: Switch gather->end to the inclusive end")
Signed-off-by: Xiang Chen <chenxiang66@...ilicon.com>
Acked-by: Will Deacon <will@...nel.org>
Link: https://lore.kernel.org/r/1616643504-120688-1-git-send-email-chenxiang66@hisilicon.com
Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 include/linux/iommu.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 5e7fe519430a..9ca6e6b8084d 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -547,7 +547,7 @@ static inline void iommu_iotlb_gather_add_page(struct iommu_domain *domain,
 	 * structure can be rewritten.
 	 */
 	if (gather->pgsize != size ||
-	    end < gather->start || start > gather->end) {
+	    end + 1 < gather->start || start > gather->end + 1) {
 		if (gather->pgsize)
 			iommu_iotlb_sync(domain, gather);
 		gather->pgsize = size;
-- 
2.30.2