On Tue, Aug 27, 2019 at 11:02:19AM +0800, Pingfan Liu wrote: > v1 -> v2: fix compile warning and error on x86_32 > > > This series include two related groups: > [1-3/4]: protect nr_cpus from rebooting by broadcast mce > [4/4]: improve "kexec -l" robustness against broadcast mce > > When I tried to fix [1], Thomas raised concern about the nr_cpus' vulnerability > to unexpected rebooting by broadcast mce. After analysis, I think only the > following first case suffers from the rebooting by broadcast mce. [1-3/4] aims > to fix that issue. > > *** Back ground *** > > On x86 it's required to have all logical CPUs set CR4.MCE=1. Otherwise, a > broadcast MCE observing CR4.MCE=0b on any core will shutdown the machine. > > The option 'nosmt' has already complied with the above rule by Thomas's patch. > For detail, refer to 506a66f3748 (Revert "x86/apic: Ignore secondary threads if > nosmt=force") > > But for nr_cpus option, the exposure to broadcast MCE is a little complicated, > and can be categorized into three cases. One thing is not clear to me: are you "fixing" a hypothetical case here or have you *actually* experienced an MCE happening while kdumping with nr_cpus < num_online_cpus()? Btw, pls do not use lkml.org to refer to previous mails but http://lkml.kernel.org/r/<Message-ID> Thx. -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply. _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
