From: Lu Baolu <baolu.lu@linux.intel.com>
To: iommu@lists.linux.dev
Cc: Kevin Tian <kevin.tian@intel.com>, Yi Liu <yi.l.liu@intel.com>,
Jacob Pan <jacob.jun.pan@linux.intel.com>,
Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
linux-kernel@vger.kernel.org, Lu Baolu <baolu.lu@linux.intel.com>
Subject: [PATCH v3 1/1] iommu/vt-d: Remove caching mode check before device TLB flush
Date: Mon, 15 Apr 2024 09:38:35 +0800 [thread overview]
Message-ID: <20240415013835.9527-1-baolu.lu@linux.intel.com> (raw)
The Caching Mode (CM) of the Intel IOMMU indicates if the hardware
implementation caches not-present or erroneous translation-structure
entries except for the first-stage translation. The caching mode is
irrelevant to the device TLB, therefore there is no need to check it
before a device TLB invalidation operation.
Remove two caching mode checks before device TLB invalidation in the
driver. The removal of these checks doesn't change the driver's behavior
in critical map/unmap paths. Hence, there is no functionality or
performance impact, especially since commit <29b32839725f> ("iommu/vt-d:
Do not use flush-queue when caching-mode is on") has already disabled
flush-queue for caching mode. Therefore, caching mode will never call
intel_flush_iotlb_all().
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
---
drivers/iommu/intel/iommu.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)
Change log:
v3:
- It turned out that the removals don't change the driver's behavior,
hence change it from a fix patch to a cleanup one.
- No functionality changes.
v2: https://lore.kernel.org/lkml/20240410055823.264501-1-baolu.lu@linux.intel.com/
- Squash two patches into a single one.
- No functionality changes.
v1: https://lore.kernel.org/linux-iommu/20240407144232.190355-1-baolu.lu@linux.intel.com/
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index a7ecd90303dc..f0a67e9d9faf 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1501,11 +1501,7 @@ static void iommu_flush_iotlb_psi(struct intel_iommu *iommu,
else
__iommu_flush_iotlb_psi(iommu, did, pfn, pages, ih);
- /*
- * In caching mode, changes of pages from non-present to present require
- * flush. However, device IOTLB doesn't need to be flushed in this case.
- */
- if (!cap_caching_mode(iommu->cap) || !map)
+ if (!map)
iommu_flush_dev_iotlb(domain, addr, mask);
}
@@ -1579,8 +1575,7 @@ static void intel_flush_iotlb_all(struct iommu_domain *domain)
iommu->flush.flush_iotlb(iommu, did, 0, 0,
DMA_TLB_DSI_FLUSH);
- if (!cap_caching_mode(iommu->cap))
- iommu_flush_dev_iotlb(dmar_domain, 0, MAX_AGAW_PFN_WIDTH);
+ iommu_flush_dev_iotlb(dmar_domain, 0, MAX_AGAW_PFN_WIDTH);
}
if (dmar_domain->nested_parent)
--
2.34.1
next reply other threads:[~2024-04-15 1:39 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-15 1:38 Lu Baolu [this message]
2024-04-15 2:22 ` [PATCH v3 1/1] iommu/vt-d: Remove caching mode check before device TLB flush Zhang, Tina
2024-04-15 2:43 ` Yi Liu
2024-04-15 5:00 ` Baolu Lu
2024-04-15 6:56 ` Yi Liu
2024-04-16 3:00 ` Baolu Lu
2024-04-17 3:40 ` Yi Liu
2024-04-16 0:53 ` Ethan Zhao
2024-04-16 2:57 ` Baolu Lu
2024-04-16 6:30 ` Ethan Zhao
2024-04-24 3:41 ` Baolu Lu
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