[Qemu-devel] [Bug 1777232] [NEW] NVME fails on big writes

[Shimi Gersner]

Public bug reported:

NVME Compliance test 8:3.3.0 tries to write and read back big chunks of
pages. Currently, on the latest QEMU operation of size 1024 blocks will
fail when device is backed by a file.

NVME specification has several types of data transfers from guests, one
of the is the PRP list (Physical Region Page List). PRP is a list of
entries pointing to pages to be written. The list it self resides in a
single or multiple pages.

NVME device maps the PRP list into QEMUSGList which will be me mapped
into linux IO vectors. Finally, when the file driver will write the
changes, it uses the posix pwritev, which fails if the number of vectors
exceeds the maximum.


NVME Compliance - https://github.com/nvmecompliance/tnvme/wiki

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1777232

Title:
  NVME fails on big writes

Status in QEMU:
  New

Bug description:
  NVME Compliance test 8:3.3.0 tries to write and read back big chunks
  of pages. Currently, on the latest QEMU operation of size 1024 blocks
  will fail when device is backed by a file.

  NVME specification has several types of data transfers from guests,
  one of the is the PRP list (Physical Region Page List). PRP is a list
  of entries pointing to pages to be written. The list it self resides
  in a single or multiple pages.

  NVME device maps the PRP list into QEMUSGList which will be me mapped
  into linux IO vectors. Finally, when the file driver will write the
  changes, it uses the posix pwritev, which fails if the number of
  vectors exceeds the maximum.

  
  NVME Compliance - https://github.com/nvmecompliance/tnvme/wiki

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