On 2021-06-07 19:25, Nadav Amit wrote:
From: Nadav Amit <na...@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 <j...@8bytes.org>
Cc: Will Deacon <w...@kernel.org>
Cc: Jiajun Cao <caojia...@vmware.com>
Cc: Robin Murphy <robin.mur...@arm.com>
Cc: Lu Baolu <baolu...@linux.intel.com>
Cc: iommu@lists.linux-foundation.org
Cc: linux-ker...@vger.kernel.org
Signed-off-by: Nadav Amit <na...@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");
Nit: you can just use pr_warn() (or arguably pr_info()) since the
explicit conditions already only match once. Speaking of which, it might
be better to use amd_iommu_np_cache instead, since other patches are
planning to clean up the last remnants of amd_iommu_unmap_flush.
Robin.
+
amd_iommu_np_cache = true;
+ amd_iommu_unmap_flush = true;
+ }
init_iommu_perf_ctr(iommu);
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