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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Chris Wilson <chris@chris-wilson.co.uk>,
	Thomas Gleixner <tglx@linutronix.de>, Bandan Das <bsd@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 22/26] Revert "x86/apic: Include the LDR when clearing out APIC registers"
Date: Sun,  8 Sep 2019 13:42:01 +0100	[thread overview]
Message-ID: <20190908121110.627865125@linuxfoundation.org> (raw)
In-Reply-To: <20190908121057.216802689@linuxfoundation.org>

[ Upstream commit 950b07c14e8c59444e2359f15fd70ed5112e11a0 ]

This reverts commit 558682b5291937a70748d36fd9ba757fb25b99ae.

Chris Wilson reports that it breaks his CPU hotplug test scripts.  In
particular, it breaks offlining and then re-onlining the boot CPU, which
we treat specially (and the BIOS does too).

The symptoms are that we can offline the CPU, but it then does not come
back online again:

    smpboot: CPU 0 is now offline
    smpboot: Booting Node 0 Processor 0 APIC 0x0
    smpboot: do_boot_cpu failed(-1) to wakeup CPU#0

Thomas says he knows why it's broken (my personal suspicion: our magic
handling of the "cpu0_logical_apicid" thing), but for 5.3 the right fix
is to just revert it, since we've never touched the LDR bits before, and
it's not worth the risk to do anything else at this stage.

[ Hotpluging of the boot CPU is special anyway, and should be off by
  default. See the "BOOTPARAM_HOTPLUG_CPU0" config option and the
  cpu0_hotplug kernel parameter.

  In general you should not do it, and it has various known limitations
  (hibernate and suspend require the boot CPU, for example).

  But it should work, even if the boot CPU is special and needs careful
  treatment       - Linus ]

Link: https://lore.kernel.org/lkml/156785100521.13300.14461504732265570003@skylake-alporthouse-com/
Reported-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Bandan Das <bsd@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/kernel/apic/apic.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 37666c5367415..928ffdc21873c 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1067,10 +1067,6 @@ void clear_local_APIC(void)
 	apic_write(APIC_LVT0, v | APIC_LVT_MASKED);
 	v = apic_read(APIC_LVT1);
 	apic_write(APIC_LVT1, v | APIC_LVT_MASKED);
-	if (!x2apic_enabled()) {
-		v = apic_read(APIC_LDR) & ~APIC_LDR_MASK;
-		apic_write(APIC_LDR, v);
-	}
 	if (maxlvt >= 4) {
 		v = apic_read(APIC_LVTPC);
 		apic_write(APIC_LVTPC, v | APIC_LVT_MASKED);
-- 
2.20.1




  parent reply	other threads:[~2019-09-08 12:44 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-08 12:41 [PATCH 4.9 00/26] 4.9.192-stable review Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 01/26] net: tundra: tsi108: use spin_lock_irqsave instead of spin_lock_irq in IRQ context Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 02/26] net: tc35815: Explicitly check NET_IP_ALIGN is not zero in tc35815_rx Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 03/26] Bluetooth: btqca: Add a short delay before downloading the NVM Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 04/26] ibmveth: Convert multicast list size for little-endian system Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 05/26] gpio: Fix build error of function redefinition Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 06/26] cxgb4: fix a memory leak bug Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 07/26] net: myri10ge: fix memory leaks Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 08/26] cx82310_eth: fix a memory leak bug Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 09/26] net: kalmia: fix memory leaks Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 10/26] wimax/i2400m: fix a memory leak bug Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 11/26] ravb: Fix use-after-free ravb_tstamp_skb Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 12/26] Tools: hv: kvp: eliminate may be used uninitialized warning Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 13/26] IB/mlx4: Fix memory leaks Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 14/26] ceph: fix buffer free while holding i_ceph_lock in __ceph_setxattr() Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 15/26] ceph: fix buffer free while holding i_ceph_lock in fill_inode() Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 16/26] KVM: arm/arm64: Only skip MMIO insn once Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 17/26] libceph: allow ceph_buffer_put() to receive a NULL ceph_buffer Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 18/26] spi: bcm2835aux: ensure interrupts are enabled for shared handler Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 19/26] spi: bcm2835aux: unifying code between polling and interrupt driven code Greg Kroah-Hartman
2019-09-08 12:41 ` [PATCH 4.9 20/26] spi: bcm2835aux: remove dangerous uncontrolled read of fifo Greg Kroah-Hartman
2019-09-08 12:42 ` [PATCH 4.9 21/26] spi: bcm2835aux: fix corruptions for longer spi transfers Greg Kroah-Hartman
2019-09-08 12:42 ` Greg Kroah-Hartman [this message]
2019-09-08 12:42 ` [PATCH 4.9 23/26] net: fix skb use after free in netpoll Greg Kroah-Hartman
2019-09-08 12:42 ` [PATCH 4.9 24/26] net: stmmac: dwmac-rk: Dont fail if phy regulator is absent Greg Kroah-Hartman
2019-09-08 12:42 ` [PATCH 4.9 25/26] tcp: inherit timestamp on mtu probe Greg Kroah-Hartman
2019-09-08 12:42 ` [PATCH 4.9 26/26] mld: fix memory leak in mld_del_delrec() Greg Kroah-Hartman
2019-09-08 16:38 ` [PATCH 4.9 00/26] 4.9.192-stable review kernelci.org bot
2019-09-09  1:33 ` Naresh Kamboju
2019-09-09 14:49 ` Bharath Vedartham
2019-09-09 19:43 ` Guenter Roeck
2019-09-10  9:19 ` Jon Hunter

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