nvme: adding support for Apple's NVMe controller

Adding support for Apple's NVMe controller. Patches are tested on linux-4.3 on a MacBook8,1. /dev/nvme0n1p* are recognized, bulk transfers work, and the previous patches have been confirmed to work on NVMe-based MacBookAir7,1 (see patches for details).

Stephan G?nther (2):
nvme: enforce ordered split transfers
nvme: add pci device id for Apple NVMe controller

 drivers/block/nvme-core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

Some controllers may require ordered split transfers even on 64bit machines, e.g. Apple's NVMe controller as found in the MacBook8,1 and MacBookAir7,1 (256/512GB models).

This patch enforces ordered split transfers on 64bit platforms, which works around that issue for all controllers. As pointed out by Christoph
[1] there should be no performance impact due to that modification.

[1] http://lists.infradead.org/pipermail/linux-nvme/2015-November/002965.html

---
 drivers/block/nvme-core.c | 8 ++++++++
 1 file changed, 8 insertions(+)

index ccc0c1f..2f1766b 100644
@@ -43,6 +43,14 @@
 #include <scsi/sg.h>
 #include <asm-generic/io-64-nonatomic-lo-hi.h>
 
+/*
+ * Some controllers may require ordered split transfers even on 64bit
+ * platforms, e.g. Apple's NVMe controller as found in the MacBook8,1 and
+ * MacBookAir7,1 (256/512GB models).
+ */
+#define readq lo_hi_readq
+#define writeq lo_hi_writeq
+
 #define NVME_MINORS		(1U << MINORBITS)
 #define NVME_Q_DEPTH		1024
 #define NVME_AQ_DEPTH		256

Add PCI ID of Apple's NVMe controller.

---
 drivers/block/nvme-core.c | 1 +
 1 file changed, 1 insertion(+)

index 2f1766b..ed088cf 100644
@@ -3326,6 +3326,7 @@ static const struct pci_error_handlers nvme_err_handler = {
 
 static const struct pci_device_id nvme_id_table[] = {
 	{ PCI_DEVICE_CLASS(PCI_CLASS_STORAGE_EXPRESS, 0xffffff) },
+	{ PCI_DEVICE(PCI_VENDOR_ID_APPLE, 0x2001) },
 	{ 0, }
 };
 MODULE_DEVICE_TABLE(pci, nvme_id_table);

Looks fine,

So far I had 2 feedbacks regarding controller resets and data loss using the patch while debootstrapping or using a partition as root file system.

Might be that controller properties exported to userspace are subject to the same issue with 64bit atomic operations like the NVMe module itself.

We will further investigate those problems in our spare time, and of course welcome any suggestions what might cause those issues.

Although I was not able to reproduce the problem so far (there is also a firmware upgrade going on with OSX 10.11.2), I must point out more I did before that using our Apple NVMe patch might cause data loss if being used careless.

Added for 4.4.

Jens Axboe