From: Nadav Amit Date: Fri, 23 Jul 2021 02:32:04 -0700 Subject: iommu/amd: Do not use flush-queue when NpCache is on Git-commit: 6664340cf1d541c2a44d588002893f795ab4143f Patch-mainline: v5.15-rc1 References: bsc#1192202 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 Cc: Will Deacon Cc: Jiajun Cao Cc: Robin Murphy Cc: Lu Baolu Cc: iommu@lists.linux-foundation.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Nadav Amit Link: https://lore.kernel.org/r/20210723093209.714328-3-namit@vmware.com Signed-off-by: Joerg Roedel --- drivers/iommu/amd/init.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/drivers/iommu/amd/init.c +++ b/drivers/iommu/amd/init.c @@ -1849,8 +1849,13 @@ static int __init iommu_init_pci(struct 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);