In D23541#516975, @mjg wrote:

In that case what about the console spam? I presume messages of this sort:

g_vfs_done():md10a[UNKNOWN()]error = 45

stem precisely from this. This happens to really spam the console for me when e.g., running stress2 when at least for this case it should never print anything. iow it looks like a design error that that devices which don't support something can get a request AND fail resulting in an error message.
Here is an example from pho's log: https://people.freebsd.org/~pho/stress/log/mark125.txt

In D23541#516964, @imp wrote:

In D23541#516955, @scottl wrote:

I agree with Alexander, I really don't like that this perpetuates bad design.

So the proper fix is to fix all the disk drivers to just return op not supported?

I agree with Alexander, I really don't like that this perpetuates bad design.

Also, this should be MFC'd to 12 and even 11. With that, you can remove in 13 instead of waiting for 14

My recommendation is to change the rotating and unmapped sysctls to be SYSCTL_PROC, and have them read the flag. That way you can retire the fields out of the softc now.

Change function names for better consistency. Add bus_dma_template_clone().
Update the man page.

I also have an large update to bus_dma.9 that I'll add to the review.

I already changed the names in an upcoming revision; I agree that simple wasn't a good name. For the purposes of cloning an existing tag, what I'd propose is to have a function, bus_dma_template_clone(*template, *dmat) that serializes the opaque fields of the tag back into a template, then lets you optionally modify the template, and then turn it into a new tag with bus_dma_template_tag(*template, *tag). I'll code that up and submit it in the next patch.

Switch to a typedef for the template. Be type-correct with
NULL field assignments.

Add ObsoleteFiles

Minor request, if the MSR_OP_LOCAL/SCHED/RENDEVOUS opcodes are mutually exclusive from each other then don't make them be bitfield definitions, just have them be sequential numbers.

This looks great. My only complaint is using the name "tweak", I think it's too casual and poorly descriptive. Maybe x86_program_msr_smp()?

Move taa into its own sysctl node, machdep.mitigations.taa.(enable|state)

Move the sysctls and tunables to the new machdep.mitigations
tree. Rename the code in accordance, and rename the sysctls
themselves to have neutral wording.

Address several comments

My suggestion is to move ssb, mds, tsx, and probably others from _hw to something like _hw.x86.mitigations. Then rename each with a name that's not enable or disable. We would still have compat OIDs, and I think that the values could remain the same. That's work for a future time, though.

Add some bootverbose messages for when things don't behave.
Track MDS state and synchronize more closely with it.

Remove an unncessary XXX comment

Forgot to set the TSX MSR on all CPUs, not just the one that's currently
running. Fixed.

Complete the TAA mitigation. Code is tested with and without the
microcode update. Has not been tested to see if it actually stops
the POC attacks.

Small updates