Messages in this thread | | | Subject | Re: 2f47e7e19f ("x86/mm/kaiser: Use PCID feature to make user and .."): WARNING: CPU: 0 PID: 1 at mm/early_ioremap.c:114 __early_ioremap | From | Dave Hansen <> | Date | Mon, 27 Nov 2017 17:22:02 -0800 |
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I think I narrowed this down.
__native_flush_tlb_single() depends on cpu_tlbstate.loaded_mm_asid matching what is in CR3. But, while we are still "early" in boot, CR3 has hardware ASID=0, but cpu_tlbstate.loaded_mm_asid=0 which is actually hardware ASID=1.
So, we have ASID=0 in CR3 and we try to *flush* ASID=1 with INVPCID, which does nothing for us, effectively missing the TLB flush.
I think we need to steer __native_flush_tlb_single() into the "!this_cpu_has(X86_FEATURE_INVPCID_SINGLE)" path if we get called before initialize_tlbstate_and_flush() gives us a "real" ASID in CR3, but I haven't found a nice way to do it, yet.
We probably also need a debugging warning in there to read CR3 and check it against cpu_tlbstate.loaded_mm_asid. I'll look at this in some more detail tomorrow if nobody beats me to it.
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