[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] x86/XPTI: fix S3 resume (and CPU offlining in general)
>>> On 24.05.18 at 16:14, <simon@xxxxxxxxxxxxxxxxxxxxxx> wrote: > Jan Beulich: >>>>> On 24.05.18 at 16:00, <simon@xxxxxxxxxxxxxxxxxxxxxx> wrote: >>> Jan Beulich: >>>> In commit d1d6fc97d6 ("x86/xpti: really hide almost all of Xen image") >>>> I've failed to remember the fact that multiple CPUs share a stub >>>> mapping page. Therefore it is wrong to unconditionally zap the mapping >>>> when bringing down a CPU; it may only be unmapped when no other online >>>> CPU uses that same page. >>>> >>>> Reported-by: Simon Gaiser <simon@xxxxxxxxxxxxxxxxxxxxxx> >>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> >>>> >>>> --- a/xen/arch/x86/smpboot.c >>>> +++ b/xen/arch/x86/smpboot.c >>>> @@ -876,7 +876,21 @@ static void cleanup_cpu_root_pgt(unsigne >>>> >>>> free_xen_pagetable(rpt); >>>> >>>> - /* Also zap the stub mapping for this CPU. */ >>>> + /* >>>> + * Also zap the stub mapping for this CPU, if no other online one uses >>>> + * the same page. >>>> + */ >>>> + if ( stub_linear ) >>>> + { >>>> + unsigned int other; >>>> + >>>> + for_each_online_cpu(other) >>>> + if ( !((per_cpu(stubs.addr, other) ^ stub_linear) >> >>>> PAGE_SHIFT) ) >>>> + { >>>> + stub_linear = 0; >>>> + break; >>>> + } >>>> + } >>>> if ( stub_linear ) >>>> { >>>> l3_pgentry_t *l3t = l4e_to_l3e(common_pgt); >>> >>> Tried this on-top of staging (fc5805daef) and I still get the same >>> double fault. >> >> Hmm, it worked for me offlining (and later re-onlining) several pCPU-s. What >> size a system are you testing on? Mine has got only 12 CPUs, i.e. all stubs >> are in the same page (and I'd never unmap anything here at all). > > 4 cores + HT, so 8 CPUs from Xen's PoV. May I ask you to do two things: 1) confirm that you can offline CPUs successfully using xen-hptool, 2) add a printk() to the code above making clear whether/when any of the mappings actually get zapped? Thanks, Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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