Messages in this thread | | | Subject | Re: [PATCH] x86/paravirt: Add missing noinstr to arch_local*() helpers | From | Jürgen Groß <> | Date | Fri, 7 Aug 2020 11:24:26 +0200 |
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On 07.08.20 11:01, Marco Elver wrote: > On Thu, 6 Aug 2020 at 18:06, Marco Elver <elver@google.com> wrote: >> On Thu, 6 Aug 2020 at 15:17, Marco Elver <elver@google.com> wrote: >>> On Thu, Aug 06, 2020 at 01:32PM +0200, peterz@infradead.org wrote: >>>> On Thu, Aug 06, 2020 at 09:47:23AM +0200, Marco Elver wrote: >>>>> Testing my hypothesis that raw then nested non-raw >>>>> local_irq_save/restore() breaks IRQ state tracking -- see the reproducer >>>>> below. This is at least 1 case I can think of that we're bound to hit. >>> ... >>>> >>>> /me goes ponder things... >>>> >>>> How's something like this then? >>>> >>>> --- >>>> include/linux/sched.h | 3 --- >>>> kernel/kcsan/core.c | 62 ++++++++++++++++++++++++++++++++++++--------------- >>>> 2 files changed, 44 insertions(+), 21 deletions(-) >>> >>> Thank you! That approach seems to pass syzbot (also with >>> CONFIG_PARAVIRT) and kcsan-test tests. >>> >>> I had to modify it some, so that report.c's use of the restore logic >>> works and not mess up the IRQ trace printed on KCSAN reports (with >>> CONFIG_KCSAN_VERBOSE). >>> >>> I still need to fully convince myself all is well now and we don't end >>> up with more fixes. :-) If it passes further testing, I'll send it as a >>> real patch (I want to add you as Co-developed-by, but would need your >>> Signed-off-by for the code you pasted, I think.) > > I let it run on syzbot through the night, and it's fine without > PARAVIRT (see below). I have sent the patch (need your Signed-off-by > as it's based on your code, thank you!): > https://lkml.kernel.org/r/20200807090031.3506555-1-elver@google.com > >> With CONFIG_PARAVIRT=y (without the notrace->noinstr patch), I still >> get lockdep DEBUG_LOCKS_WARN_ON(!lockdep_hardirqs_enabled()), although >> it takes longer for syzbot to hit them. But I think that's expected >> because we can still get the recursion that I pointed out, and will >> need that patch. > > Never mind, I get these warnings even if I don't turn on KCSAN > (CONFIG_KCSAN=n). Something else is going on with PARAVIRT=y that > throws off IRQ state tracking. :-/
What are the settings of CONFIG_PARAVIRT_XXL and CONFIG_PARAVIRT_SPINLOCKS in this case?
Juergen
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