linux-kernel - [PATCH] nvme/pci: remap BAR0 to cover admin CQ doorbell for large stride

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Date:   Thu, 18 May 2017 06:35:47 +0800
From:   Xu Yu <yu.a.xu@...el.com>
To:     linux-nvme@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, keith.busch@...el.com, axboe@...com,
        hch@....de, sagi@...mberg.me, yu.a.xu@...el.com,
        haozhong.zhang@...el.com
Subject: [PATCH] nvme/pci: remap BAR0 to cover admin CQ doorbell for large stride

The existing driver initially maps 8192 bytes of BAR0 which is
intended to cover doorbells of admin SQ and CQ. However, if a
large stride, e.g. 10, is used, the doorbell of admin CQ will
be out of 8192 bytes. Consequently, a page fault will be raised
when the admin CQ doorbell is accessed in nvme_configure_admin_queue().

This patch fixes this issue by remapping BAR0 before accessing
admin CQ doorbell if the initial mapping is not enough.

Signed-off-by: "Xu, Yu A" <yu.a.xu@...el.com>
---
 drivers/nvme/host/pci.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 9d4640a..7c991eb 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1322,6 +1322,17 @@ static int nvme_configure_admin_queue(struct nvme_dev *dev)
 	u32 aqa;
 	u64 cap = lo_hi_readq(dev->bar + NVME_REG_CAP);
 	struct nvme_queue *nvmeq;
+	struct pci_dev *pdev = to_pci_dev(dev->dev);
+	unsigned long size;
+
+	size = 4096 + 2 * 4 * dev->db_stride;
+	if (size > 8192) {
+		iounmap(dev->bar);
+		dev->bar = ioremap(pci_resource_start(pdev, 0), size);
+		if (!dev->bar)
+			return -ENOMEM;
+		dev->dbs = dev->bar + 4096;
+	}
 
 	dev->subsystem = readl(dev->bar + NVME_REG_VS) >= NVME_VS(1, 1, 0) ?
 						NVME_CAP_NSSRC(cap) : 0;
-- 
2.10.1