On Mon, Jun 19, 2023 at 05:57:14PM +0200, Jan Beulich wrote: > > + * We might have exposed MSR_ARCH_CAPS after the microcode update. > > I'm struggling a little with this sentence, but not being a native speaker > it may be me, not the sentence. I would perhaps have said "MSR_ARCH_CAPS > may have appeared with the microcode update." Sure, works for me.
> I also wonder whether you wouldn't want to insert "e.g.", since iirc with > the next patch tsx_init() isn't going to be the only user anymore. tsx_init() is the only user, as far as I have seen. DIS_MCU_LOAD is checked before the update, using the cached data read in early_cpu_init() > > > + */ > > + if ( boot_cpu_data.cpuid_level >= 7 ) > > + boot_cpu_data.x86_capability[FEATURESET_7d0] > > + = cpuid_count_edx(7, 0); > > I take it we assume the maximum CPUID level won't go from below 7 to 7 > or higher with the ucode update? Do you mean from >=7 to <7 instead? Otherwise it just works and I don't undertand the concern. If so, that's an impossibly unlikely case and the current code does not try to clean up in that case. > > > --- a/xen/arch/x86/tsx.c > > +++ b/xen/arch/x86/tsx.c > > @@ -39,9 +39,9 @@ void tsx_init(void) > > static bool __read_mostly once; > > > > /* > > - * This function is first called between microcode being loaded, and > > CPUID > > - * being scanned generally. Read into boot_cpu_data.x86_capability[] > > for > > - * the cpu_has_* bits we care about using here. > > + * This function is first called between microcode being loaded, and > > + * CPUID being scanned generally. early_microcode_init() has already > > + * prepared the feature bits needed here after the microcode update. > > Is this true in all cases? early_microcode_init() may have bailed > early, so I think you need to further transform early_microcode_init() > (and as a personal request of mine preferably without goto). > > Jan The series is eventually correct because MSR_ARCH_CAPS are also collected in early_cpu_init(). Alas, that's not the case here. You're right. I'll move the early MSR_ARCH_CAPS read to this patch as well. Alejandro
