Messages in this thread | | | Date | Wed, 16 Aug 2023 09:07:57 -0700 | From | Josh Poimboeuf <> | Subject | Re: [PATCH] x86/srso: Correct the mitigation status when SMT is disabled |
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On Wed, Aug 16, 2023 at 10:30:57AM +0200, Borislav Petkov wrote: > On Tue, Aug 15, 2023 at 02:27:51PM -0700, Josh Poimboeuf wrote: > > How is that relevant to my comment? The bug bit still wouldn't get set > > and srso_show_state() still wouldn't be called. > > Lemme explain how I see this working - it might help us get on the right > track. And for comparison you can look at X86_FEATURE_BTC_NO too. > > * Something has set X86_FEATURE_SRSO_NO - hw or sw doesn't matter > - because the machine is not affected. X86_BUG_SRSO doesn't get set and > the mitigation detection is skipped. All good.
In this case srso_show_state() is never called, so the following code can't run:
+ if (boot_cpu_has(X86_FEATURE_SRSO_NO)) { + if (sched_smt_active()) + return sysfs_emit(buf, "Not affected\n");
> * Nothing has set X86_FEATURE_SRSO_NO, mitigation detection runs and > find that the kernel runs on a Zen1/2 with SMT disabled - we set > X86_FEATURE_SRSO_NO.
In this case SMT is disabled, so the following code still can't run:
+ if (boot_cpu_has(X86_FEATURE_SRSO_NO)) { + if (sched_smt_active()) + return sysfs_emit(buf, "Not affected\n");
So the above code never runs.
See?
-- Josh
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