Messages in this thread | | | From | Andy Lutomirski <> | Subject | Re: [patch 13/16] x86/entry: Move irqflags and context tracking to C for simple idtentries | Date | Wed, 26 Feb 2020 09:09:34 -0800 |
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> On Feb 26, 2020, at 9:05 AM, Frederic Weisbecker <frederic@kernel.org> wrote: > > On Wed, Feb 26, 2020 at 09:05:38AM +0100, Peter Zijlstra wrote: >>> On Tue, Feb 25, 2020 at 11:33:34PM +0100, Thomas Gleixner wrote: >>> >>> --- a/arch/x86/include/asm/idtentry.h >>> +++ b/arch/x86/include/asm/idtentry.h >>> @@ -7,14 +7,31 @@ >>> >>> #ifndef __ASSEMBLY__ >>> >>> +#ifdef CONFIG_CONTEXT_TRACKING >>> +static __always_inline void enter_from_user_context(void) >>> +{ >>> + CT_WARN_ON(ct_state() != CONTEXT_USER); >>> + user_exit_irqoff(); >>> +} >>> +#else >>> +static __always_inline void enter_from_user_context(void) { } >>> +#endif >>> + >>> /** >>> * idtentry_enter - Handle state tracking on idtentry >>> * @regs: Pointer to pt_regs of interrupted context >>> * >>> - * Place holder for now. >>> + * Invokes: >>> + * - The hardirq tracer to keep the state consistent as low level ASM >>> + * entry disabled interrupts. >>> + * >>> + * - Context tracking if the exception hit user mode >>> */ >>> static __always_inline void idtentry_enter(struct pt_regs *regs) >>> { >>> + trace_hardirqs_off(); >>> + if (user_mode(regs)) >>> + enter_from_user_context(); >>> } >> >> So: >> >> asm_exc_int3 >> exc_int3 >> idtentry_enter() >> enter_from_user_context >> if (context_tracking_enabled()) >> >> poke_int3_handler(); >> >> Is, AFAICT, completely buggered. >> >> You can't have a static_branch before the poke_int3_handler that deals >> with text_poke. > > #BP is treated like an NMI in your patchset IIRC? > In that case and since that implies we can't schedule, we can remove > the call to context tracking there once we have nmi_enter()/nmi_exit() > called unconditionally.
int3 from user mode can send signals. This has better be able to schedule by the time it hits prepare_exit_to_usermode.
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