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bhyve: nvme set Abort Command Limit (ACL) and Asynchronous Event Request Limit (AERL) values as specfication suggested
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Authored by wanpengqian_gmail.com on Aug 25 2022, 5:04 AM.
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imp
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bhyve
Summary

Currently the acl and aerl are set to values 3 and 5. as specificaton's recommendation, these values are 4.

Test Plan

Do a nvmecontrol identify from guest. check the output result.

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rG FreeBSD src repository
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Build 44077: arc lint + arc unit

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wanpengqian_gmail.com retitled this revision from Set Abort Command Limit (ACL) and Asynchronous Event Request Limit (AERL) values as specfica ton suggested. to bhyve: nvme set Abort Command Limit (ACL) and Asynchronous Event Request Limit (AERL) values as specfication suggested.Aug 25 2022, 5:06 AM
wanpengqian_gmail.com edited the summary of this revision. (Show Details)
usr.sbin/bhyve/pci_nvme.c
545–546

There isn't a limit on the number of concurrent aborts in the implementation. So one arbitrary value is as good as another, but I'd suggest removing the comment.

546

The wording in the specification is:

It is recommended that implementations support a minimum of four Asynchronous
Event Request Limit commands outstanding simultaneously.

Supporting 5 (aerl = 4) would meet their recommendation, wouldn't you agree?

usr.sbin/bhyve/pci_nvme.c
545–546

You are right, currently the Abort Command is not processed by the controller. I'd like the value to be more normal as real nvme controllers use the specification recommended value. I will remove the comment later.

546

Yes, a value higher than 4 is totally OK as specification says. but the value of 5 is a little un-normal. I don't know why we pick up this value at first. as 4 is the value that other controllers do as far as my observation.