Messages in this thread | | | Subject | Re: [RFC PATCH 2/4] x86/entry/nmi: Use normal idtentry macro for NMI from userspace | From | Andy Lutomirski <> | Date | Thu, 3 Jun 2021 10:36:19 -0700 |
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On 5/31/21 11:52 PM, Lai Jiangshan wrote: > From: Lai Jiangshan <laijs@linux.alibaba.com> > > Before tglx made huge refactor on entry code, high level code is called > from ASM code including idtentry exit path which might reopen IRQ, > reschedule, do signal among other works and made normal entry path not > suitable for userspace NMI entry. So when the commit 9b6e6a8334d56 > ("x86/nmi/64: Switch stacks on userspace NMI entry") added special code > for userspace NMI entry, it didn't use normal entry code. > > After the said refactor on entry code, high level code was moved into > C code, and the idtentry macros are really low level and fit for > userspace NMI entry after it switches to entry stack, so this > patch uses idtentry_body macro for NMI from userspace. > > Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> > --- > arch/x86/entry/entry_64.S | 42 ++++++--------------------------------- > 1 file changed, 6 insertions(+), 36 deletions(-) > > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S > index 4190e668f346..f54e06139d4b 100644 > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -1113,11 +1113,7 @@ SYM_CODE_START(asm_exc_nmi) > jz .Lnmi_from_kernel > > /* > - * NMI from user mode. We need to run on the thread stack, but we > - * can't go through the normal entry paths: NMIs are masked, and > - * we don't want to enable interrupts, because then we'll end > - * up in an awkward situation in which IRQs are on but NMIs > - * are off. > + * NMI from user mode. We need to run on the thread stack.
This comment is IMO still important, but I think you're right that it no longer matters in the asm. Could you relocate the comment to the appropriate place in the C code so that a future cleanup doesn't mess up the C path?
Thanks, Andy
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