linux kernel 5.12.5支持NVMe1.4 CMB功能

在最新的kernel 5.12.5终于看到对NVMe 1.4协议的CMB支持了，喜大普奔！散花散花！
NVMe 1.4协议的CMB功能变化太大了，增加了CMBS，CRE，CMBMSC，CMBSTS。看起来终于像一个像样的功能了。
kernel驱动一直跟不上，这次驱动更新终于更新到这一块了，不枉我天天在我的dnvme驱动上修修补补。。。
PMR也抓紧跟上。。。

static void nvme_map_cmb(struct nvme_dev *dev)
{
	u64 size, offset;
	resource_size_t bar_size;
	struct pci_dev *pdev = to_pci_dev(dev->dev);
	int bar;

	if (dev->cmb_size)
		return;

	if (NVME_CAP_CMBS(dev->ctrl.cap))
		writel(NVME_CMBMSC_CRE, dev->bar + NVME_REG_CMBMSC);

	dev->cmbsz = readl(dev->bar + NVME_REG_CMBSZ);
	if (!dev->cmbsz)
		return;
	dev->cmbloc = readl(dev->bar + NVME_REG_CMBLOC);

	size = nvme_cmb_size_unit(dev) * nvme_cmb_size(dev);
	offset = nvme_cmb_size_unit(dev) * NVME_CMB_OFST(dev->cmbloc);
	bar = NVME_CMB_BIR(dev->cmbloc);
	bar_size = pci_resource_len(pdev, bar);

	if (offset > bar_size)
		return;

	/*
	 * Tell the controller about the host side address mapping the CMB,
	 * and enable CMB decoding for the NVMe 1.4+ scheme:
	 */
	if (NVME_CAP_CMBS(dev->ctrl.cap)) {
		hi_lo_writeq(NVME_CMBMSC_CRE | NVME_CMBMSC_CMSE |
			     (pci_bus_address(pdev, bar) + offset),
			     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");
		return;
	}

	dev->cmb_size = size;
	dev->cmb_use_sqes = use_cmb_sqes && (dev->cmbsz & NVME_CMBSZ_SQS);

	if ((dev->cmbsz & (NVME_CMBSZ_WDS | NVME_CMBSZ_RDS)) ==
			(NVME_CMBSZ_WDS | NVME_CMBSZ_RDS))
		pci_p2pmem_publish(pdev, true);

	if (sysfs_add_file_to_group(&dev->ctrl.device->kobj,
				    &dev_attr_cmb.attr, NULL))
		dev_warn(dev->ctrl.device,
			 "failed to add sysfs attribute for CMB\n");
}