Tim,
On Tue, 30 Oct 2018, Tim Chen wrote:
> Extract the logic to show IBPB, STIBP usages in cpu_show_common()
> into helper functions.
>
> Later patches will add other userspace Spectre v2 mitigation modes.
> This patch makes it easy to show IBPB and STIBP
> usage scenario according to the mitigation mode.
First of all, I asked you before to do:
# git grep 'This patch' Documentation/process
This leads you to:
"Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
to do frotz", as if you are giving orders to the codebase to change
its behaviour."
Documentation is there for a reason.
Aside of that, I'd really have a hard time to figure out what you are
trying to say, if I didn't have the context already. Change logs need to
make sense on their own. So something like this:
The Spectre V2 printout in cpu_show_common() handles conditionals for the
various mitigation methods directly in the sprintf() argument list. That's
hard to read and will become unreadable if more complex decisions need to
be made for a particular method.
Move the conditionals for STIBP and IBPB string selection into helper
functions, so they can be extended later on.
follows the obvious ordering for change logs:
1) Describe context and problem
2) Describe the solution
and is understandable without needing to know about the context in which
this change was developed.
Hmm? This is a suggestion, feel free to rewrite it in you own words. The
same applies to other change logs as well. I won't comment on those.
> static ssize_t cpu_show_common(struct device *dev, struct device_attribute
> *attr,
> char *buf, unsigned int bug)
> {
> @@ -872,9 +888,8 @@ static ssize_t cpu_show_common(struct device *dev, struct
> device_attribute *attr
>
> case X86_BUG_SPECTRE_V2:
> return sprintf(buf, "%s%s%s%s%s%s\n",
> spectre_v2_strings[spectre_v2_enabled],
> - boot_cpu_has(X86_FEATURE_USE_IBPB) ? ", IBPB" :
> "",
> boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ",
> IBRS_FW" : "",
> - (x86_spec_ctrl_base & SPEC_CTRL_STIBP) ? ",
> STIBP" : "",
> + ibpb_state(), stibp_state(),
> boot_cpu_has(X86_FEATURE_RSB_CTXSW) ? ", RSB
> filling" : "",
> spectre_v2_module_string());
Any particular reason for changing the output ordering here? If yes, then
the changelog should mention it. If no, why?
Thanks,
tglx
