Messages in this thread |  | | Date | Mon, 30 Mar 2020 07:26:48 -0700 | From | Sean Christopherson <> | Subject | Re: [PATCH v7 1/2] x86/split_lock: Rework the initialization flow of split lock detection |
| |
On Mon, Mar 30, 2020 at 09:26:25PM +0800, Xiaoyao Li wrote: > On 3/29/2020 12:32 AM, Sean Christopherson wrote: > >On Wed, Mar 25, 2020 at 11:09:23AM +0800, Xiaoyao Li wrote: > >> static void split_lock_init(void) > >> { > >>- if (sld_state == sld_off) > >>- return; > >>- > >>- if (__sld_msr_set(true)) > >>- return; > >>- > >>- /* > >>- * If this is anything other than the boot-cpu, you've done > >>- * funny things and you get to keep whatever pieces. > >>- */ > >>- pr_warn("MSR fail -- disabled\n"); > >>- sld_state = sld_off; > >>+ split_lock_verify_msr(sld_state != sld_off); > > > >I think it'd be worth a WARN_ON() if this fails with sld_state != off. If > >the WRMSR fails, then presumably SLD is off when it's expected to be on. > >The implied WARN on the unsafe WRMSR in sld_update_msr() won't fire unless > >a task generates an #AC on a non-buggy core and then gets migrated to the > >buggy core. Even if the WARNs are redundant, if something is wrong it'd be > >a lot easier for a user to triage/debug if there is a WARN in boot as > >opposed to a runtime WARN that requires a misbehaving application and > >scheduler behavior. > > > > IIUC, you're recommending something like below? > > WARN_ON(!split_lock_verify_msr(sld_state != sld_off) && > sld_state != sld_off);
Ya.
|  |