On 08/04/2019 12:38, Julien Grall wrote: > Hi, > > On 4/8/19 11:47 AM, Andrew Cooper wrote: >> On 08/04/2019 11:39, Julien Grall wrote: >>> Hi, >>> >>> On 4/8/19 10:39 AM, Andrew Cooper wrote: >>>> + case CPU_RESUME_FAILED: >>>> + if ( !park_offline_cpus && system_state != >>>> SYS_STATE_suspend ) >>> >>> This patch breaks compilation on arm32/arm64 because park_offline_cpus >>> is not defined: >>> >>> timer.c: In function 'cpu_callback': >>> timer.c:651:15: error: 'park_offline_cpus' undeclared (first use in >>> this function) >>> if ( !park_offline_cpus && system_state != >>> SYS_STATE_suspend ) >>> ^~~~~~~~~~~~~~~~~ >>> >>> What is the purpose of park_offline_cpus? >> >> Sorry. I should have waited for a full build test first. >> >> park_offline_cpus is a workaround for Intel's MCE behaviour, where the >> system will shut down rather than deliver an #MC if machine checking >> isn't configured on all CPUs. >> >> As a result, we have to start all CPUs, even beyond maxcpus= and set up >> machine check handling, and never ever free their stacks, even if we'd >> prefer the CPUs to be offline. > > I am a bit confused, why this is necessary now for the timer and not > in other places of the common code? > >> >> Are you happy with a >> >> #define park_offline_cpus false > >> in ARM? > > The name is fairly confusing if you don't know the background. > > But I have to admit that even with your explanation above, I still > don't understand why you need to check park_offline_cpus in the timers.
It is all to do with how/when we free per-cpu data. Technically speaking (with the memory leak fixed) the old arrangement ought to function correctly, but the new arrangement is more efficient. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
