linux-kernel - [tip: x86/apic] x86/ioapic: Prevent inconsistent state when moving an interrupt

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Date:   Thu, 24 Oct 2019 10:13:11 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/apic] x86/ioapic: Prevent inconsistent state when moving an
 interrupt

The following commit has been merged into the x86/apic branch of tip:

Commit-ID:     df4393424af3fbdcd5c404077176082a8ce459c4
Gitweb:        https://git.kernel.org/tip/df4393424af3fbdcd5c404077176082a8ce459c4
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Thu, 17 Oct 2019 12:19:01 +02:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Thu, 24 Oct 2019 12:09:21 +02:00

x86/ioapic: Prevent inconsistent state when moving an interrupt

There is an issue with threaded interrupts which are marked ONESHOT
and using the fasteoi handler:

  if (IS_ONESHOT())
    mask_irq();
  ....
  cond_unmask_eoi_irq()
    chip->irq_eoi();
      if (setaffinity_pending) {
         mask_ioapic();
         ...
	 move_affinity();
	 unmask_ioapic();
      }

So if setaffinity is pending the interrupt will be moved and then
unconditionally unmasked at the ioapic level, which is wrong in two
aspects:

 1) It should be kept masked up to the point where the threaded handler
    finished.

 2) The physical chip state and the software masked state are inconsistent

Guard both the mask and the unmask with a check for the software masked
state. If the line is marked masked then the ioapic line is also masked, so
both mask_ioapic() and unmask_ioapic() can be skipped safely.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Sebastian Siewior <bigeasy@...utronix.de>
Fixes: 3aa551c9b4c4 ("genirq: add threaded interrupt handler support")
Link: https://lkml.kernel.org/r/20191017101938.321393687@linutronix.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/apic/io_apic.c |  9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index d6af97f..f0262cb 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -1727,9 +1727,10 @@ static bool io_apic_level_ack_pending(struct mp_chip_data *data)
 
 static inline bool ioapic_irqd_mask(struct irq_data *data)
 {
-	/* If we are moving the irq we need to mask it */
+	/* If we are moving the IRQ we need to mask it */
 	if (unlikely(irqd_is_setaffinity_pending(data))) {
-		mask_ioapic_irq(data);
+		if (!irqd_irq_masked(data))
+			mask_ioapic_irq(data);
 		return true;
 	}
 	return false;
@@ -1766,7 +1767,9 @@ static inline void ioapic_irqd_unmask(struct irq_data *data, bool masked)
 		 */
 		if (!io_apic_level_ack_pending(data->chip_data))
 			irq_move_masked_irq(data);
-		unmask_ioapic_irq(data);
+		/* If the IRQ is masked in the core, leave it: */
+		if (!irqd_irq_masked(data))
+			unmask_ioapic_irq(data);
 	}
 }
 #else