Messages in this thread Patch in this message |  | | From | Nadav Amit <> | Subject | [PATCH 4/4] iommu/amd: Do not use flush-queue when NpCache is on | Date | Sun, 2 May 2021 00:00:01 -0700 |
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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: 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 d006724f4dc2..ba3b76ed776d 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_warn_once("IOMMU batching is disabled due to virtualization"); + amd_iommu_np_cache = true; + amd_iommu_unmap_flush = true; + } init_iommu_perf_ctr(iommu); -- 2.25.1
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