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iommu/amd: Do not use flush-queue when NpCache is on 

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 29b3283972
("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>
Link: https://lore.kernel.org/r/20210723093209.714328-3-namit@vmware.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Nadav Amit 2021-07-23 02:32:04 -07:00 committed by Joerg Roedel
parent fc65d0acaf
commit 6664340cf1
1 changed files with 6 additions and 1 deletions
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7
drivers/iommu/amd/init.c
View File

@ -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);