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[PATCH 4.9 21/93] powerpc/64: Fix __check_irq_replay missing decrementer interrupt

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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nicholas Piggin <npiggin@gmail.com>

commit 3db40c312c2c1eb2187c5731102fa8ff380e6e40 upstream.

If the decrementer wraps again and de-asserts the decrementer
exception while hard-disabled, __check_irq_replay() has a test to
notice the wrap when interrupts are re-enabled.

The decrementer check must be done when clearing the PACA_IRQ_HARD_DIS
flag, not when the PACA_IRQ_DEC flag is tested. Previously this worked
because the decrementer interrupt was always the first one checked
after clearing the hard disable flag, but HMI check was moved ahead of
that, which introduced this bug.

This can cause a missed decrementer interrupt if we soft-disable
interrupts then take an HMI which is recorded in irq_happened, then
hard-disable interrupts for > 4s to wrap the decrementer.

Fixes: e0e0d6b7390b ("powerpc/64: Replay hypervisor maintenance interrupt first")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/powerpc/kernel/irq.c |   15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -146,6 +146,19 @@ notrace unsigned int __check_irq_replay(
 
 	/* Clear bit 0 which we wouldn't clear otherwise */
 	local_paca->irq_happened &= ~PACA_IRQ_HARD_DIS;
+	if (happened & PACA_IRQ_HARD_DIS) {
+		/*
+		 * We may have missed a decrementer interrupt if hard disabled.
+		 * Check the decrementer register in case we had a rollover
+		 * while hard disabled.
+		 */
+		if (!(happened & PACA_IRQ_DEC)) {
+			if (decrementer_check_overflow()) {
+				local_paca->irq_happened |= PACA_IRQ_DEC;
+				happened |= PACA_IRQ_DEC;
+			}
+		}
+	}
 
 	/*
 	 * Force the delivery of pending soft-disabled interrupts on PS3.
@@ -171,7 +184,7 @@ notrace unsigned int __check_irq_replay(
 	 * in case we also had a rollover while hard disabled
 	 */
 	local_paca->irq_happened &= ~PACA_IRQ_DEC;
-	if ((happened & PACA_IRQ_DEC) || decrementer_check_overflow())
+	if (happened & PACA_IRQ_DEC)
 		return 0x900;
 
 	/* Finally check if an external interrupt happened */

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[PATCH 4.9 00/93] 4.9.42-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 23/93] gpiolib: skip unwanted events, dont convert them to opposite edge Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 19/93] timers: Fix overflow in get_next_timer_interrupt Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 26/93] ARM: dts: armada-38x: Fix irq type for pca955 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 06/93] iwlwifi: dvm: prevent an out of bounds access Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 41/93] ipv4: ipv6: initialize treq->txhash in cookie_v[46]_check() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 37/93] tcp_bbr: introduce bbr_bw_to_pacing_rate() helper Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 10/93] device property: Make dev_fwnode() public Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 40/93] tcp_bbr: init pacing rate on first RTT sample Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 11/93] mmc: core: Fix access to HS400-ES devices Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 21/93] powerpc/64: Fix __check_irq_replay missing decrementer interrupt Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 36/93] tcp_bbr: cut pacing rate only if filled pipe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 12/93] mm, mprotect: flush TLB if potentially racing with a parallel reclaim leaving stale TLB entries Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 24/93] ext4: fix SEEK_HOLE/SEEK_DATA for blocksize < pagesize Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 20/93] powerpc/tm: Fix saving of TM SPRs in core dump Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 33/93] f2fs: sanity check checkpoint segno and blkoff Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 29/93] iscsi-target: Fix initial login PDU asynchronous socket close OOPs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 35/93] [media] saa7164: fix double fetch PCIe access condition Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 32/93] media: lirc: LIRC_GET_REC_RESOLUTION should return microseconds Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 01/93] parisc: Handle vmas whose context is not current in flush_cache_range Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 44/93] net: dsa: b53: Add missing ARL entries for BCM53125 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 08/93] NFSv4: Fix EXCHANGE_ID corrupt verifier issue Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  [PATCH 4.9 43/93] ipv6: avoid overflow of offset in ip6_find_1stfragopt Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-09 20:40 +0200
  Re: [PATCH 4.9 00/93] 4.9.42-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-08-10 02:20 +0200
  Re: [PATCH 4.9 00/93] 4.9.42-stable review Guenter Roeck <linux@roeck-us.net> - 2017-08-10 02:50 +0200
  Re: [PATCH 4.9 00/93] 4.9.42-stable review Sumit Semwal <sumit.semwal@linaro.org> - 2017-08-10 05:10 +0200

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