Messages in this thread | | | Subject | Re: [PATCH 1/2] x86/mm/pat: Change pat_disable() to emulate PAT table | From | Toshi Kani <> | Date | Fri, 11 Mar 2016 09:27:40 -0700 |
| |
On Fri, 2016-03-11 at 09:12 +0000, Borislav Petkov wrote: > On Thu, Mar 10, 2016 at 09:45:45PM -0700, Toshi Kani wrote: : > > > > -static inline void pat_disable(const char *reason) > > +void pat_disable(const char *reason) > > { > > + if (boot_cpu_done) { > > + pr_info("x86/PAT: PAT cannot be disabled after > > initialized\n"); > > pr_err()
Will do.
> > > + return; > > + } > > + > > __pat_enabled = 0; > > pr_info("x86/PAT: %s\n", reason); > > + > > + pat_disable_init(); > > Why can't you call pat_init() here simply? It checks pat_enabled(). You > can call it pat_setup() or so if it looks confusing to call an init > function in a disable function...
How about pat_disable_setup()? It's only used for the disabled case, so I'd prefer to keep the word "disable".
Yes, calling pat_init() from pat_disable() works too. I changed it in this way because: - pat_bsp_init() calls pat_disabled() in an error case. It is simpler to avoid a recursive call to pat_init(). - pat_bsp_init() has two different error paths, 1) call pat_disable() and return, and 2) goto done and call pat_init_cache_modes(). We can remove case 2) to keep the error handling consistent in this way.
> Then you don't have to add yet another static disable_init_done but rely > on boot_cpu_done which gets set in pat_init().
Right, but it will do 'boot_cpu_done = true' twice, and this implicit recursive call may cause an issue in future if someone makes change carelessly.
> Also, I don't see the static_cpu_has() check I suggested yesterday - we > need to check the feature bits if PAT gets disabled early on some old > Intels.
Sorry, I should have mentioned it. I ended up not needing this change. The table in patch 2/2 covers this case as:
MTRR PAT ACTION ==================================================================== E D MTRR calls pat_init() -> PAT disabled per cpu_has_pat
That is, the check with cpu_has_pat in pat_bsp_init() calls pat_disable() in this case. I preferred this way because it will continue to log a message "PAT not supported by CPU.", and keeps __pat_enabled as the single variable to manage the PAT state.
Thanks, -Toshi
| |