Commits on Dec 7, 2023

1. Implement a nvme driver …

   The implemented driver allows OSv to boot from a emulated nvme device and
   handle additional nvme devices, emulated or passed through from the host.
   Booting directly from a nvme via pci-passthrough needs to be tested.
   
   The nvme driver creates nvme_queue_pairs to interact with the device
   controller. A nvme_queue_pair manages a submission queue and the
   corresponding completion queue.
   The nvme driver registers every namespace as device and forwards requests
   to the queues. Namespace 1 on the first nvme drive is named "vblk0".
   Further devices are named nvmeXnY where X is the driver instance id
   starting with 0 and Y is the namespace id starting with 1.
   
   Read/Write requests on the device file go through the block cache layer.
   This can reduce performance quite a bit, since the block cache splits
   every request into 512B-sized sequentiell requests. Setting
   NVME_DIRECT_RW_ENABLED in /drivers/nvme.hh disables the block cache.
   
   All queues use MSI-X. 1 interrupt vector gets registered for every queue.
   There is very noticeable overhead while using pci-passthrough. This gets
   reduced by using interrupt coalescing but needs to be further investigated.
   
   Add options to ./scripts/run.py:
   --nvme to start OSv on a nvme emulated by QEMU
   --second-nvme-image to attach an additional image as nvme
   --pass-pci to passthrough a pci device from the host
       the device needs to be bound to vfio-pci
   
   drivers/blk_ioctl.hh implements the BLKGETSIZE64 and BLKFLSBUF
   ioctl which are used by fio
   
   drivers/io-test.cc is an simple iops test that can be activated by
   building with conf_drivers_io_test=1 and runs during initialization
   of the nvme device
   
   Signed-off-by: Jan Braunwarth <jan.braunwarth@gmail.com>

   

   JanBraunwarth committed Dec 7, 2023
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