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 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>
Link: https://lore.kernel.org/r/20210723093209.714328-3-namit@vmware.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 46280e6..1c7ae7d 100644 (file)
--- 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);