| Message ID | 1548084825-8803-25-git-send-email-julien.thierry@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: provide pseudo NMI with GICv3 | expand |
On Mon, 21 Jan 2019 15:33:43 +0000, Julien Thierry <julien.thierry@arm.com> wrote: > > Handling of an NMI should not set any TIF flags. For NMIs received from > EL0 the current exit path is safe to use. > > However, an NMI received at EL1 could have interrupted some task context > that has set the TIF_NEED_RESCHED flag. Preempting a task should not > happen as a result of an NMI. > > Skip preemption after handling an NMI from EL1. > > Signed-off-by: Julien Thierry <julien.thierry@arm.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Marc Zyngier <marc.zyngier@arm.com> > --- > arch/arm64/kernel/entry.S | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S > index 35a47f6..a0b0a22 100644 > --- a/arch/arm64/kernel/entry.S > +++ b/arch/arm64/kernel/entry.S > @@ -624,6 +624,14 @@ el1_irq: > > #ifdef CONFIG_PREEMPT > ldr x24, [tsk, #TSK_TI_PREEMPT] // get preempt count > +alternative_if ARM64_HAS_IRQ_PRIO_MASKING > + /* > + * DA_F were cleared at start of handling. If anything is set in DAIF, > + * we come back from an NMI, so skip preemption > + */ > + mrs x0, daif > + orr x24, x24, x0 > +alternative_else_nop_endif > cbnz x24, 1f // preempt count != 0 > bl el1_preempt > 1: I find this a bit ugly, as what we have in x24 is not the preempt count anymore. Maybe amend the comment above? The code being nonetheless correct: Acked-by: Marc Zyngier <marc.zyngier@arm.com> M.
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 35a47f6..a0b0a22 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -624,6 +624,14 @@ el1_irq: #ifdef CONFIG_PREEMPT ldr x24, [tsk, #TSK_TI_PREEMPT] // get preempt count +alternative_if ARM64_HAS_IRQ_PRIO_MASKING + /* + * DA_F were cleared at start of handling. If anything is set in DAIF, + * we come back from an NMI, so skip preemption + */ + mrs x0, daif + orr x24, x24, x0 +alternative_else_nop_endif cbnz x24, 1f // preempt count != 0 bl el1_preempt 1:
Handling of an NMI should not set any TIF flags. For NMIs received from EL0 the current exit path is safe to use. However, an NMI received at EL1 could have interrupted some task context that has set the TIF_NEED_RESCHED flag. Preempting a task should not happen as a result of an NMI. Skip preemption after handling an NMI from EL1. Signed-off-by: Julien Thierry <julien.thierry@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Marc Zyngier <marc.zyngier@arm.com> --- arch/arm64/kernel/entry.S | 8 ++++++++ 1 file changed, 8 insertions(+)