Gilles Chanteperdrix wrote: > Jan Kiszka wrote: >> If we enter __ipipe_handle_exception over a non-root domain and leave it >> due to migration in the event handler over root, we must not restore the >> root domain state so far saved on entry. This caused subtle pipeline >> state corruptions. Actually, we only need to save the state if we enter >> over the root domain and have to align its state to the hardware >> interrupt mask. >> >> Moreover, the x86-32 regs.eflags fix-up must happen based on the current >> root domain state to avoid more spurious corruptions. >> >> Signed-off-by: Jan Kiszka <[email protected]> >> --- >> >> This patch is so far running fine on the x86-64 boxes of our colleagues >> @Healthcare. It currently makes most sense to me, also for (untested) >> x86-32, but maybe I'm still missing a problematic scenario. >> >> arch/x86/kernel/ipipe.c | 64 >> ++++++++++++++++++++++++++-------------------- >> 1 files changed, 36 insertions(+), 28 deletions(-) >> >> diff --git a/arch/x86/kernel/ipipe.c b/arch/x86/kernel/ipipe.c >> index 4442d96..8253993 100644 >> --- a/arch/x86/kernel/ipipe.c >> +++ b/arch/x86/kernel/ipipe.c >> @@ -702,19 +702,17 @@ static int __ipipe_xlate_signo[] = { >> >> int __ipipe_handle_exception(struct pt_regs *regs, long error_code, int >> vector) >> { >> - unsigned long flags; >> - >> - /* Pick up the root domain state of the interrupted context. */ >> - local_save_flags(flags); >> + bool restore_flags = false; >> + unsigned long flags = 0; >> >> - if (ipipe_root_domain_p) { >> + if (ipipe_root_domain_p && irqs_disabled_hw()) { > > I really do not understand this hunk. It differs a lot from the current > situation. In the current situation __fixup_if really does something, > even if irqs were not masked on entry. >
This hunk is no longer related to __fixup_if. The latter now picks up the information about what to fix from root domain state _after_ the return of the ipipe exception hook. That way we avoid leaking the wrong root state on entry over a non-root domain after migration within the hook. Jan
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