On 11.02.2022 11:47, Roger Pau Monné wrote: > On Fri, Feb 11, 2022 at 11:32:45AM +0100, Jan Beulich wrote: >> On 11.02.2022 10:02, Roger Pau Monné wrote: >>> On Fri, Feb 11, 2022 at 08:23:27AM +0100, Norbert Manthey wrote: >>>> When re-identifying CPU data, we might use uninitialized data when >>>> checking for the cache line property to adapt the cache >>>> alignment. The data that depends on this uninitialized read is >>>> currently not forwarded. >>>> >>>> To avoid problems in the future, initialize the data cpuinfo >>>> structure before re-identifying the CPU again. >>>> >>>> The trace to hit the uninitialized read reported by Coverity is: >>>> >>>> bool recheck_cpu_features(unsigned int cpu) >>>> ... >>>> struct cpuinfo_x86 c; >>>> ... >>>> identify_cpu(&c); >>>> >>>> void identify_cpu(struct cpuinfo_x86 *c) >>>> ... >>>> generic_identify(c) >>>> >>>> static void generic_identify(struct cpuinfo_x86 *c) >>>> ... >>> >>> Would it be more appropriate for generic_identify to also set >>> x86_cache_alignment like it's done in early_cpu_init? >>> >>> generic_identify already re-fetches a bunch of stuff that's also >>> set by early_cpu_init for the BSP. >> >> This would be an option, but how sure are you that there isn't >> (going to be) another field with similar properties? We better >> wouldn't require _everything_ to be re-filled in generic_identify(). > > So you think generic_identify should call into early_cpu_init, or even > split the cpuinfo_x86 filling done in early_cpu_init into a non-init > function that could be called by both generic_identify and > early_cpu_init?
No, I think it is quite fine for this to be a two-step process. In fact I was hoping to eliminate some of the remaining redundancy where possible. recheck_cpu_features(), after all, cares about just the feature flags, so doesn't require things like cache line alignment to be filled in. Jan
