Date: Thu, 29 Jul 2010 02:50:08 GMT From: Joe Landers <jlanders@vmware.com> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/148698: [panic] Panic at boot due to integer overflow computing top->cg_mask in smp_topo_none() when mp_ncpus == 32 Message-ID: <201007290250.o6T2o83B000507@freefall.freebsd.org>
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The following reply was made to PR kern/148698; it has been noted by GNATS.
From: Joe Landers <jlanders@vmware.com>
To: "bug-followup@FreeBSD.org" <bug-followup@FreeBSD.org>, Joe Landers
<jlanders@vmware.com>
Cc:
Subject: Re: kern/148698: [panic] Panic at boot due to integer overflow
computing top->cg_mask in smp_topo_none() when mp_ncpus == 32
Date: Wed, 28 Jul 2010 19:26:19 -0700
We understand that > 32 CPUs isn't possible with the current code structure=
.
However, it is trivial to make the case of mp_ncpus =3D=3D 32 work.
Assuming no error checking, simply change the computation of top->cg_mask f=
rom:
top->cg_mask =3D (1 << mp_ncpus) - 1;
to:
top->cg_mask =3D ~0U >> (32 - mp_ncpus);
in subr_smp.c:smp_topo_none().
FreeBSD will then boot fine with 32 or fewer CPUs:
...
FreeBSD/SMP: Multiprocessor System Detected: 32 CPUs
FreeBSD/SMP: 32 package(s) x 1 core(s)
cpu0 (BSP): APIC ID: 0
cpu1 (AP): APIC ID: 1
cpu2 (AP): APIC ID: 2
cpu3 (AP): APIC ID: 3
cpu4 (AP): APIC ID: 4
cpu5 (AP): APIC ID: 5
cpu6 (AP): APIC ID: 6
cpu7 (AP): APIC ID: 7
cpu8 (AP): APIC ID: 8
cpu9 (AP): APIC ID: 9
cpu10 (AP): APIC ID: 10
cpu11 (AP): APIC ID: 11
cpu12 (AP): APIC ID: 12
cpu13 (AP): APIC ID: 13
cpu14 (AP): APIC ID: 14
cpu15 (AP): APIC ID: 15
cpu16 (AP): APIC ID: 16
cpu17 (AP): APIC ID: 17
cpu18 (AP): APIC ID: 18
cpu19 (AP): APIC ID: 19
cpu20 (AP): APIC ID: 20
cpu21 (AP): APIC ID: 21
cpu22 (AP): APIC ID: 22
cpu23 (AP): APIC ID: 23
cpu24 (AP): APIC ID: 24
cpu25 (AP): APIC ID: 25
cpu26 (AP): APIC ID: 26
cpu27 (AP): APIC ID: 27
cpu28 (AP): APIC ID: 28
cpu29 (AP): APIC ID: 29
cpu30 (AP): APIC ID: 30
cpu31 (AP): APIC ID: 31
ioapic0: Changing APIC ID to 32
...
SMP: AP CPU #28 Launched!
SMP: AP CPU #27 Launched!
SMP: AP CPU #1 Launched!
SMP: AP CPU #2 Launched!
SMP: AP CPU #31 Launched!
SMP: AP CPU #3 Launched!
SMP: AP CPU #13 Launched!
SMP: AP CPU #23 Launched!
SMP: AP CPU #4 Launched!
SMP: AP CPU #9 Launched!
SMP: AP CPU #20 Launched!
SMP: AP CPU #21 Launched!
SMP: AP CPU #5 Launched!
SMP: AP CPU #12 Launched!
SMP: AP CPU #15 Launched!
SMP: AP CPU #16 Launched!
SMP: AP CPU #7 Launched!
SMP: AP CPU #26 Launched!
SMP: AP CPU #29 Launched!
SMP: AP CPU #17 Launched!
SMP: AP CPU #25 Launched!
SMP: AP CPU #6 Launched!
SMP: AP CPU #11 Launched!
SMP: AP CPU #19 Launched!
SMP: AP CPU #14 Launched!
SMP: AP CPU #18 Launched!
SMP: AP CPU #22 Launched!
SMP: AP CPU #10 Launched!
SMP: AP CPU #24 Launched!
SMP: AP CPU #8 Launched!
SMP: AP CPU #30 Launched!
...
We verified this fix on both physical and virtual hardware.
Thanks,
Joe Landers
jlanders@vmware.com
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