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From: "Jan Beulich" <JBeulich@suse.com>
To: "xen-devel" <xen-devel@lists.xenproject.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>, Wei Liu <wl@xen.org>,
	Roger Pau Monne <roger.pau@citrix.com>
Subject: [Xen-devel] [PATCH] x86/SMP: don't try to stop already stopped CPUs
Date: Wed, 29 May 2019 04:17:49 -0600
Message-ID: <5CEE5C4D02000078002335A0@prv1-mh.provo.novell.com> (raw)
Message-ID: <20190529101749.H2kxnfizK77hKHHJ3IzNZKKLTFrbs-Ke2o66BEoWDlM@z> (raw)

In particular with an enabled IOMMU (but not really limited to this
case), trying to invoke fixup_irqs() after having already done
disable_IO_APIC() -> clear_IO_APIC() is a rather bad idea:

 RIP:    e008:[<ffff82d08026a036>] amd_iommu_read_ioapic_from_ire+0xde/0x113
 RFLAGS: 0000000000010006   CONTEXT: hypervisor (d0v0)
 rax: ffff8320291de00c   rbx: 0000000000000003   rcx: ffff832035000000
 rdx: 0000000000000000   rsi: 0000000000000000   rdi: ffff82d0805ca840
 rbp: ffff83009e8a79c8   rsp: ffff83009e8a79a8   r8:  0000000000000000
 r9:  0000000000000004   r10: 000000000008b9f9   r11: 0000000000000006
 r12: 0000000000010000   r13: 0000000000000003   r14: 0000000000000000
 r15: 00000000fffeffff   cr0: 0000000080050033   cr4: 00000000003406e0
 cr3: 0000002035d59000   cr2: ffff88824ccb4ee0
 fsb: 00007f2143f08840   gsb: ffff888256a00000   gss: 0000000000000000
 ds: 0000   es: 0000   fs: 0000   gs: 0000   ss: e010   cs: e008
 Xen code around <ffff82d08026a036> (amd_iommu_read_ioapic_from_ire+0xde/0x113):
  ff 07 00 00 39 d3 74 02 <0f> 0b 41 81 e4 00 f8 ff ff 8b 10 89 d0 25 00 00
 Xen stack trace from rsp=ffff83009e8a79a8:
 ...
 Xen call trace:
    [<ffff82d08026a036>] amd_iommu_read_ioapic_from_ire+0xde/0x113
    [<ffff82d08026bf7b>] iommu_read_apic_from_ire+0x10/0x12
    [<ffff82d08027f718>] io_apic.c#modify_IO_APIC_irq+0x5e/0x126
    [<ffff82d08027f9c5>] io_apic.c#unmask_IO_APIC_irq+0x2d/0x41
    [<ffff82d080289bc7>] fixup_irqs+0x320/0x40b
    [<ffff82d0802a82c4>] smp_send_stop+0x4b/0xa8
    [<ffff82d0802a7b2f>] machine_restart+0x98/0x288
    [<ffff82d080252242>] console_suspend+0/0x28
    [<ffff82d0802b01da>] do_general_protection+0x204/0x24e
    [<ffff82d080385a3d>] x86_64/entry.S#handle_exception_saved+0x68/0x94
    [<00000000aa5b526b>] 00000000aa5b526b
    [<ffff82d0802a7c7d>] machine_restart+0x1e6/0x288
    [<ffff82d080240f75>] hwdom_shutdown+0xa2/0x11d
    [<ffff82d08020baa2>] domain_shutdown+0x4f/0xd8
    [<ffff82d08023fe98>] do_sched_op+0x12f/0x42a
    [<ffff82d08037e404>] pv_hypercall+0x1e4/0x564
    [<ffff82d080385432>] lstar_enter+0x112/0x120

Don't call fixup_irqs() and don't send any IPI if there's only one
online CPU anyway, and don't call __stop_this_cpu() at all when the CPU
we're on was already marked offline (by a prior invocation of
__stop_this_cpu()).

Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/smp.c
+++ b/xen/arch/x86/smp.c
@@ -302,23 +302,31 @@ static void stop_this_cpu(void *dummy)
  */
 void smp_send_stop(void)
 {
-    int timeout = 10;
+    unsigned int cpu = smp_processor_id();
 
-    local_irq_disable();
-    fixup_irqs(cpumask_of(smp_processor_id()), 0);
-    local_irq_enable();
-
-    smp_call_function(stop_this_cpu, NULL, 0);
-
-    /* Wait 10ms for all other CPUs to go offline. */
-    while ( (num_online_cpus() > 1) && (timeout-- > 0) )
-        mdelay(1);
-
-    local_irq_disable();
-    disable_IO_APIC();
-    hpet_disable();
-    __stop_this_cpu();
-    local_irq_enable();
+    if ( num_online_cpus() > 1 )
+    {
+        int timeout = 10;
+
+        local_irq_disable();
+        fixup_irqs(cpumask_of(cpu), 0);
+        local_irq_enable();
+
+        smp_call_function(stop_this_cpu, NULL, 0);
+
+        /* Wait 10ms for all other CPUs to go offline. */
+        while ( (num_online_cpus() > 1) && (timeout-- > 0) )
+            mdelay(1);
+    }
+
+    if ( cpu_online(cpu) )
+    {
+        local_irq_disable();
+        disable_IO_APIC();
+        hpet_disable();
+        __stop_this_cpu();
+        local_irq_enable();
+    }
 }
 
 void smp_send_nmi_allbutself(void)





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Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-29 10:17 Jan Beulich [this message]
2019-05-29 10:17 ` Jan Beulich
2019-06-03 14:12 ` Roger Pau Monné
2019-06-03 14:12   ` [Xen-devel] " Roger Pau Monné
2019-06-03 15:40   ` Jan Beulich
2019-06-03 15:40     ` [Xen-devel] " Jan Beulich
2019-06-03 16:35     ` Roger Pau Monné
2019-06-03 16:35       ` [Xen-devel] " Roger Pau Monné
2019-06-17 17:39 ` Andrew Cooper
2019-06-17 17:55   ` Andrew Cooper
2019-06-17 18:27     ` Andrew Cooper
2019-06-18 10:26       ` Jan Beulich
2019-06-18  9:23   ` Jan Beulich

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