From 56cf7ef0d490b28fad8f8629fc135c5ab7c9f54e Mon Sep 17 00:00:00 2001
From: Icenowy Zheng <uwu@icenowy.me>
Date: Thu, 13 Feb 2025 01:04:44 +0800
Subject: [PATCH] nvme-pci: skip CMB blocks incompatible with PCI P2P DMA
The PCI P2PDMA code will register the CMB block to the memory
hot-plugging subsystem, which have an alignment requirement. Memory
blocks that do not satisfy this alignment requirement (usually 2MB) will
lead to a WARNING from memory hotplugging.
Verify the CMB block's address and size against the alignment and only
try to send CMB blocks compatible with it to prevent this warning.
Tested on Intel DC D4502 SSD, which has a 512K CMB block that is too
small for memory hotplugging (thus PCI P2PDMA).
Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
Signed-off-by: Keith Busch <kbusch@kernel.org>
---
drivers/nvme/host/pci.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 218506e3dabea..640590b217282 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1982,6 +1982,18 @@ static void nvme_map_cmb(struct nvme_dev *dev)
if (offset > bar_size)
return;
+ /*
+ * Controllers may support a CMB size larger than their BAR, for
+ * example, due to being behind a bridge. Reduce the CMB to the
+ * reported size of the BAR
+ */
+ size = min(size, bar_size - offset);
+
+ if (!IS_ALIGNED(size, memremap_compat_align()) ||
+ !IS_ALIGNED(pci_resource_start(pdev, bar),
+ memremap_compat_align()))
+ return;
+
/*
* Tell the controller about the host side address mapping the CMB,
* and enable CMB decoding for the NVMe 1.4+ scheme:
@@ -1992,14 +2004,6 @@ static void nvme_map_cmb(struct nvme_dev *dev)
dev->bar + NVME_REG_CMBMSC);
}
- /*
- * Controllers may support a CMB size larger than their BAR,
- * for example, due to being behind a bridge. Reduce the CMB to
- * the reported size of the BAR
- */
- if (size > bar_size - offset)
- size = bar_size - offset;
-
if (pci_p2pdma_add_resource(pdev, bar, size, offset)) {
dev_warn(dev->ctrl.device,
"failed to register the CMB\n");
--
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