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From: Nadav Amit <nadav.amit@gmail.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: John Garry <john.garry@huawei.com>, Nadav Amit <namit@vmware.com>,
	Will Deacon <will@kernel.org>, Jiajun Cao <caojiajun@vmware.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Lu Baolu <baolu.lu@linux.intel.com>,
	iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: [PATCH v6 2/7] iommu/amd: Do not use flush-queue when NpCache is on
Date: Fri, 23 Jul 2021 02:32:04 -0700	[thread overview]
Message-ID: <20210723093209.714328-3-namit@vmware.com> (raw)
In-Reply-To: <20210723093209.714328-1-namit@vmware.com>

From: Nadav Amit <namit@vmware.com>

Do not use flush-queue on virtualized environments, where the NpCache
capability of the IOMMU is set. This is required to reduce
virtualization overheads.

This change follows a similar change to Intel's VT-d and a detailed
explanation as for the rationale is described in commit 29b32839725f
("iommu/vt-d: Do not use flush-queue when caching-mode is on").

Cc: Joerg Roedel <joro@8bytes.org>
Cc: Will Deacon <will@kernel.org>
Cc: Jiajun Cao <caojiajun@vmware.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Lu Baolu <baolu.lu@linux.intel.com>
Cc: iommu@lists.linux-foundation.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Nadav Amit <namit@vmware.com>
---
 drivers/iommu/amd/init.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 46280e6e1535..1c7ae7d3c55d 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -1850,8 +1850,13 @@ static int __init iommu_init_pci(struct amd_iommu *iommu)
 	if (ret)
 		return ret;
 
-	if (iommu->cap & (1UL << IOMMU_CAP_NPCACHE))
+	if (iommu->cap & (1UL << IOMMU_CAP_NPCACHE)) {
+		if (!amd_iommu_unmap_flush)
+			pr_info("IOMMU batching is disabled due to virtualization\n");
+
 		amd_iommu_np_cache = true;
+		amd_iommu_unmap_flush = true;
+	}
 
 	init_iommu_perf_ctr(iommu);
 
-- 
2.25.1


  parent reply	other threads:[~2021-07-23 17:02 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-23  9:32 [PATCH v6 0/7] iommu/amd: Enable page-selective flushes Nadav Amit
2021-07-23  9:32 ` [PATCH v6 1/7] iommu/amd: Selective flush on unmap Nadav Amit
2021-07-23  9:32 ` Nadav Amit [this message]
2021-07-23  9:32 ` [PATCH v6 3/7] iommu: Improve iommu_iotlb_gather helpers Nadav Amit
2021-07-23  9:32 ` [PATCH v6 4/7] iommu: Factor iommu_iotlb_gather_is_disjoint() out Nadav Amit
2021-07-23  9:32 ` [PATCH v6 5/7] iommu/amd: Tailored gather logic for AMD Nadav Amit
2021-07-23  9:32 ` [PATCH v6 6/7] iommu/amd: Sync once for scatter-gather operations Nadav Amit
2021-07-23  9:32 ` [PATCH v6 7/7] iommu/amd: Use only natural aligned flushes in a VM Nadav Amit
2021-07-26 12:31 ` [PATCH v6 0/7] iommu/amd: Enable page-selective flushes Joerg Roedel
2021-08-02  9:26 ` Joerg Roedel

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