ebsnvme-stats: Correct numd - #56
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Per the NVMe specification: "Number of Dwords Lower (NUMDL): This field specifies the least significant 16 bits of the number of dwords to return unless otherwise specified. If the host specifies a size larger than the log page requested, the controller returns the complete log page with undefined results for dwords beyond the end of the log page, unless otherwise specified. The combined NUMDL field and NUMDU field form a 0's based value." Since the number of Dwords is 1024 (4096 / 4) and this is expressed as a *0's based value* the value which must be stored in the top 16 bits of Command Dword 10 is 1024 - 1 = 1023, not 1024. Signed-off-by: Colin Percival <cperciva@FreeBSD.org>
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I have not confirmed that EBS implements NVMe correctly (in fact, I know that it does not implement NVMe correctly in other ways...) but if EBS is bug-for-bug compatible with the previous behaviour of this command-line tool then this change should still be harmless since the only difference is whether a reserved value is copied out. I have not tested this change, since I do not use the tool in question; this bug was found purely by code inspection. |
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Per the NVMe specification:
"Number of Dwords Lower (NUMDL): This field specifies the least
significant 16 bits of the number of dwords to return unless
otherwise specified. If the host specifies a size larger than
the log page requested, the controller returns the complete log
page with undefined results for dwords beyond the end of the log
page, unless otherwise specified. The combined NUMDL field and
NUMDU field form a 0's based value."
Since the number of Dwords is 1024 (4096 / 4) and this is expressed as a 0's based value the value which must be stored in the top 16 bits of Command Dword 10 is 1024 - 1 = 1023, not 1024.
Issue #, if available:
n/a
Description of changes:
Bug fix; see commit message.
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