[Xen-devel] [PATCH] tools/libxl: add support for emulated NVMe drives

[Paul Durrant <paul.durrant@xxxxxxxxxx>]

Upstream QEMU supports emulation of NVM Express a.k.a. NVMe drives.

This patch adds a new vdev type into libxl to allow such drives to be
presented to HVM guests. Because the purpose of the new vdev is purely
to configure emulation, the syntax only supports specification of
whole disks. Also there is no need to introduce a new concrete VBD
encoding for NVMe drives.

NOTE: QEMU's emulation only supports a single NVMe namespace, so the
      vdev syntax does not include specification of a namespace.
      Also, current versions of SeaBIOS do not support booting from
      NVMe devices, so the vdev should only be used for secondary
      drives.

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
---
 docs/man/xen-vbd-interface.markdown.7 | 15 ++++++++-------
 docs/man/xl-disk-configuration.pod.5  |  4 ++--
 tools/libxl/libxl_device.c            |  8 ++++++++
 tools/libxl/libxl_dm.c                |  6 ++++++
 4 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/docs/man/xen-vbd-interface.markdown.7 
b/docs/man/xen-vbd-interface.markdown.7
index 1c996bf..8fd378c 100644
--- a/docs/man/xen-vbd-interface.markdown.7
+++ b/docs/man/xen-vbd-interface.markdown.7
@@ -8,12 +8,12 @@ emulated IDE, AHCI or SCSI disks.
 The abstract interface involves specifying, for each block device:
 
  * Nominal disk type: Xen virtual disk (aka xvd*, the default); SCSI
-   (sd*); IDE or AHCI (hd*).
+   (sd*); IDE or AHCI (hd*); NVMe.
 
-   For HVM guests, each whole-disk hd* and and sd* device is made
-   available _both_ via emulated IDE resp. SCSI controller, _and_ as a
-   Xen VBD.  The HVM guest is entitled to assume that the IDE or SCSI
-   disks available via the emulated IDE controller target the same
+   For HVM guests, each whole-disk hd*, sd* or nvme* device is made
+   available _both_ via emulated IDE, SCSI controller or NVMe drive
+   respectively _and_ as a Xen VBD.  The HVM guest is entitled to
+   assume that the disks available via the emulation target the same
    underlying devices as the corresponding Xen VBD (ie, multipath).
    In hd* case with hdtype=ahci, disk will be AHCI via emulated
    ich9 disk controller.
@@ -42,8 +42,7 @@ The abstract interface involves specifying, for each block 
device:
    treat each vbd as it would a partition or slice or LVM volume (for
    example by putting or expecting a filesystem on it).
 
-   Non-whole disk devices cannot be passed through to HVM guests via
-   the emulated IDE or SCSI controllers.
+   Only whole disk devices can be emulated for HVM guests.
 
 
 Configuration file syntax
@@ -56,6 +55,7 @@ The config file syntaxes are, for example
        d536p37  xvdtq37  Xen virtual disk 536 partition 37
        sdb3              SCSI disk 1 partition 3
        hdc2              IDE disk 2 partition 2
+       nvme0             NVMe disk 0 (whole disk only)
 
 The d*p* syntax is not supported by xm/xend.
 
@@ -78,6 +78,7 @@ encodes the information above as follows:
      8 << 8 | disk << 4 | partition      sd, disks and partitions up to 15
      3 << 8 | disk << 6 | partition      hd, disks 0..1, partitions 0..63
     22 << 8 | (disk-2) << 6 | partition  hd, disks 2..3, partitions 0..63
+    1 << 28 | disk << 8                  nvme, all disks, whole disk only
     2 << 28 onwards                      reserved for future use
    other values less than 1 << 28        deprecated / reserved
 
diff --git a/docs/man/xl-disk-configuration.pod.5 
b/docs/man/xl-disk-configuration.pod.5
index d3eedc1..c40418e 100644
--- a/docs/man/xl-disk-configuration.pod.5
+++ b/docs/man/xl-disk-configuration.pod.5
@@ -127,8 +127,8 @@ designation in some specifications).  
L<xen-vbd-interface(7)>
 
 =item Supported values
 
-hd[x], xvd[x], sd[x] etc.  Please refer to the above specification for
-further details.
+hd[x], xvd[x], sd[x], nvme[x] etc.  Please refer to the above specification
+for further details.
 
 =item Deprecated values
 
diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
index b2aeefc..63a738c 100644
--- a/tools/libxl/libxl_device.c
+++ b/tools/libxl/libxl_device.c
@@ -532,6 +532,14 @@ int libxl__device_disk_dev_number(const char *virtpath, 
int *pdisk,
         if (ppartition) *ppartition = partition;
         return (8 << 8) | (disk << 4) | partition;
     }
+    if (!memcmp(virtpath, "nvme", 4)) {
+        disk = strtoul(virtpath + 4, &ep, 10);
+        if (*ep)
+            return -1;
+        if (pdisk) *pdisk = disk;
+        if (ppartition) *ppartition = 0;
+        return (1 << 28) | (disk << 8);
+    }
     return -1;
 }
 
diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 281058d..980dad1 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -1430,6 +1430,12 @@ static int libxl__build_device_model_args_new(libxl__gc 
*gc,
                                                         format,
                                                         &disks[i],
                                                         colo_mode);
+                } else if (strncmp(disks[i].vdev, "nvme", 4) == 0) {
+                    flexarray_vappend(dm_args,
+                        "-drive",  
GCSPRINTF("file=%s,if=none,id=nvmedisk-%d,format=%s,cache=writeback", 
target_path, disk, format),
+                        "-device", 
GCSPRINTF("nvme,drive=nvmedisk-%d,serial=%d", disk, disk),
+                        NULL);
+                    continue;
                 } else if (disk < 6 && b_info->u.hvm.hdtype == 
LIBXL_HDTYPE_AHCI) {
                     if (!disks[i].readwrite) {
                         LOGD(ERROR, guest_domid,
-- 
2.1.4


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