Hot-added devices can affect the existing ones by moving their BARs. The
PCI subsystem will inform the NVME driver about this by invoking the
.rescan_prepare() and .rescan_done() hooks, so the BARs can by re-mapped.
Tested under the "randrw" mode of the fio tool, and when using an NVME
drive as a root filesystem storage. Before the hot-adding:
% sudo cat /proc/iomem
...
3fe800000000-3fe8007fffff : PCI Bus 0020:0b
3fe800000000-3fe8007fffff : PCI Bus 0020:18
3fe800000000-3fe8000fffff : 0020:18:00.0
3fe800000000-3fe8000fffff : nvme
^^^^^^^^^^^^^^^^^^^^^^^^^
3fe800100000-3fe80017ffff : 0020:18:00.0
...
Then another NVME drive was hot-added, so BARs of the 0020:18:00.0 are
moved:
% sudo cat /proc/iomem
...
3fe800000000-3fe800ffffff : PCI Bus 0020:0b
3fe800000000-3fe8007fffff : PCI Bus 0020:10
3fe800000000-3fe800003fff : 0020:10:00.0
3fe800000000-3fe800003fff : nvme
3fe800010000-3fe80001ffff : 0020:10:00.0
3fe800800000-3fe800ffffff : PCI Bus 0020:18
3fe800800000-3fe8008fffff : 0020:18:00.0
3fe800800000-3fe8008fffff : nvme
^^^^^^^^^^^^^^^^^^^^^^^^^
3fe800900000-3fe80097ffff : 0020:18:00.0
...
During the rescanning, both READ and WRITE speeds drop to zero for a while
due to driver's pause, then restore.
Cc: linux-nvme@xxxxxxxxxxxxxxxxxxx
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Sergei Miroshnichenko <s.miroshnichenko@xxxxxxxxx>
---
drivers/nvme/host/pci.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 4e79e412b276..677ded2d4dd4 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1621,7 +1621,7 @@ static int nvme_remap_bar(struct nvme_dev *dev, unsigned long size)
{
struct pci_dev *pdev = to_pci_dev(dev->dev);
- if (size <= dev->bar_mapped_size)
+ if (dev->bar && size <= dev->bar_mapped_size)
return 0;
if (size > pci_resource_len(pdev, 0))
return -ENOMEM;
@@ -3032,6 +3032,23 @@ static void nvme_error_resume(struct pci_dev *pdev)
flush_work(&dev->ctrl.reset_work);
}
+static void nvme_rescan_prepare(struct pci_dev *pdev)
+{
+ struct nvme_dev *dev = pci_get_drvdata(pdev);
+
+ nvme_dev_disable(dev, false);
+ nvme_dev_unmap(dev);
+ dev->bar = NULL;
+}
+
+static void nvme_rescan_done(struct pci_dev *pdev)
+{
+ struct nvme_dev *dev = pci_get_drvdata(pdev);
+
+ nvme_dev_map(dev);
+ nvme_reset_ctrl_sync(&dev->ctrl);
+}
+
static const struct pci_error_handlers nvme_err_handler = {
.error_detected = nvme_error_detected,
.slot_reset = nvme_slot_reset,
@@ -3110,6 +3127,8 @@ static struct pci_driver nvme_driver = {
#endif
.sriov_configure = pci_sriov_configure_simple,
.err_handler = &nvme_err_handler,
+ .rescan_prepare = nvme_rescan_prepare,
+ .rescan_done = nvme_rescan_done,
};
static int __init nvme_init(void)
--
2.24.1
