On Sat, 2016-03-12 at 12:55 +0100, Borislav Petkov wrote: > Ok, let's start again. > > So what's wrong with this simpler, cleaner version below? > > * It makes sure to run the rendezvous handler on the BP on init. > > * It disables PAT otherwise. > > * Oh, and it boots fine with Paul's reproducer, X is there (even though > vncviewer dies when X starts with "Rect too large: 640x480 at (0, 0)" > and I have to reconnect to see the X window). > > In dmesg I see "x86/PAT: Disabled by MTRR".
Your patch is a simplified version of mine. So, yes, it fixes the Paul's issue, but it does not address other issues that my patchset also addressed. In specific, I think your patch has the following issues. - pat_disable() is now callable from other modules. So, it needs to check with boot_cpu_done. We cannot disable PAT once it is initialized. - mtrr_bp_init() needs to check with mtrr_enabled() when it calls mtrr_pat_setup_bp(). Otherwise, PAT is left initialized on BSP only when MTRR is disabled by its MSR. In your patch, mtrr_bp_init() calls pat_setup() again, but it does not help since boot_cpu_done is set. - When PAT is disabled in CPU feature, pat_bsp_init() calls pat_disable() and returns. However, it does not initialize a PAT table by calling pat_init_cache_modes(). - When CONFIG_MTRR is unset, it does not call pat_setup(). Thanks, -Toshi
