public inbox for devel@edk2.groups.io
 help / color / mirror / Atom feed
* [PATCH v2 0/1] UefiScsiLib: Set FUA bit for synchronous SCSI Write operations
@ 2020-03-26  7:34 Zurcher, Christopher J
  2020-03-26  7:34 ` [PATCH v2 1/1] MdePkg/UefiScsiLib: " Zurcher, Christopher J
  0 siblings, 1 reply; 6+ messages in thread
From: Zurcher, Christopher J @ 2020-03-26  7:34 UTC (permalink / raw)
  To: devel; +Cc: Michael D Kinney, Jian J Wang, Liming Gao, Zhiguang Liu

V2 changes:
Add bit defines for cache control parameters from SBC-2.

Some SCSI devices have very aggressive write caching implemented, causing
data to be lost if the system is shut down or rebooted soon after
receiving a successful write confirmation from the device. By setting the
FUA bit in the synchronous versions of the Write10/Write16 commands, the
write cache is skipped and data is forced directly to the disk.

The Asynchronous (WriteEx) commands will not have this bit set, allowing
performance-sensitive transactions to continue utilizing the write cache.

An alternative, more complicated solution would be to implement the
SYNCHRONIZE CACHE command and call it from ScsiDiskFlushBlocks, which
currently returns EFI_SUCCESS without flushing anything. Since the
SYNCHRONIZE CACHE command requires the caller to provide the specific
blocks to flush, and the BlockIO FlushBlocks function does not accept any
arguments, this would require keeping track of the write history inside the
ScsiDiskDxe driver.

I have not tested the asynchronous commands for this issue, so there is a
chance that resetting the system even after a call to FlushBlocksEx might
still result in lost data. Currently the ScsiDiskFlushBlocksEx command
waits for the BlockIo2 requests queue to empty, but does not ask the device
itself to flush anything. (EFI_SCSI_OP_SYNC_CACHE is defined in
IndustryStandard/Scsi.h but is not implemented anywhere.)

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Zhiguang Liu <zhiguang.liu@intel.com>

Christopher J Zurcher (1):
  MdePkg/UefiScsiLib: Set FUA bit for synchronous SCSI Write operations

 MdePkg/Include/IndustryStandard/Scsi.h   |  8 +++++++-
 MdePkg/Library/UefiScsiLib/UefiScsiLib.c | 14 ++++++++------
 2 files changed, 15 insertions(+), 7 deletions(-)

-- 
2.16.2.windows.1


^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2020-04-14 15:53 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2020-03-26  7:34 [PATCH v2 0/1] UefiScsiLib: Set FUA bit for synchronous SCSI Write operations Zurcher, Christopher J
2020-03-26  7:34 ` [PATCH v2 1/1] MdePkg/UefiScsiLib: " Zurcher, Christopher J
2020-03-30  1:52   ` Zhiguang Liu
2020-03-30 13:51     ` Liming Gao
2020-03-30 20:34       ` Zurcher, Christopher J
2020-04-14 15:53         ` Liming Gao

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox