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SubjectRe: [BUG?] Xeon with HyperThreading and linux-2.4.20-rc2
On Wed, 20 Nov 2002, Steffen Persvold wrote:
> On Tue, 19 Nov 2002, Hugh Dickins wrote:
> > On Tue, 19 Nov 2002, Steffen Persvold wrote:
> > >
> > > I've two boxes with Dual Xeons 1.8 GHz and HT option enabled in BIOS. When
> > > I boot 2.4.20-rc2 with default arguments the kernel detects 4 processors and
> > > also reports 4 processors in /proc/cpuinfo wiht the "ht" feature.
> > >
> > > However, if I boot with the "noht" option (wich I believed turned off HT
> > > and therefore only two processors should be available), the kernel still
> > > detects 4 processors, _but_ now the "ht" feature in /proc/cpuinfo is not
> > > there. Is this the intention of the "noht" option ?
> >
> > No, the intention of the "noht" option is as you believed, and it used to
> > work that way. I looked at latest sourcec, didn't see anything obviously
> > wrong. Sorry, but I don't have a suitable HT machine to check at present.
> >
> > > If so, are there any
> > > options available to turn off HT support in the kernel completely, so that
> > > I don't have to go into the BIOS to turn it off ?
> > >
> > > If you want to I can provide the dmesg output and .config.
> > >
> > > I think this issue is not just related to 2.4.20-rc2, but earlier kernels
> > > aswell.
> >
> > Could others check and report if 2.4.20-rc2 "noht" works for them or not?
> >
>
> Thanks for your reply Hugh,
>
> After digging into it a bit, I _think_ I know what happens. When the
> machine is bootet with default parameters, the processors are detected in
> the ACPI table, and the MP table search is skipped :
>
> Linux version 2.4.20-rc2 (root@puma1.office.scali.no) (gcc version 3.2 20020903 (Red Hat Linux 8.0 3.2-7)) #4 SMP Sat Nov 16 14:06:13 CET 2002
> BIOS-provided physical RAM map:
> BIOS-e820: 0000000000000000 - 000000000009f400 (usable)
> BIOS-e820: 000000000009f400 - 00000000000a0000 (reserved)
> BIOS-e820: 00000000000d8000 - 00000000000e0000 (reserved)
> BIOS-e820: 00000000000e4000 - 0000000000100000 (reserved)
> BIOS-e820: 0000000000100000 - 000000003fef0000 (usable)
> BIOS-e820: 000000003fef0000 - 000000003fefc000 (ACPI data)
> BIOS-e820: 000000003fefc000 - 000000003ff00000 (ACPI NVS)
> BIOS-e820: 000000003ff00000 - 000000003ff80000 (usable)
> BIOS-e820: 000000003ff80000 - 0000000040000000 (reserved)
> BIOS-e820: 00000000fec00000 - 00000000fec10000 (reserved)
> BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
> BIOS-e820: 00000000ff800000 - 00000000ffc00000 (reserved)
> BIOS-e820: 00000000fff00000 - 0000000100000000 (reserved)
> 127MB HIGHMEM available.
> 896MB LOWMEM available.
> found SMP MP-table at 000f7030
> hm, page 000f7000 reserved twice.
> hm, page 000f8000 reserved twice.
> hm, page 0009f000 reserved twice.
> hm, page 000a0000 reserved twice.
> On node 0 totalpages: 262016
> zone(0): 4096 pages.
> zone(1): 225280 pages.
> zone(2): 32640 pages.
> ACPI: Searched entire block, no RSDP was found.
> ACPI: RSDP located at physical address c00f7090
> RSD PTR v0 [PTLTD ]
> __va_range(0x3fef84e0, 0x68): idx=8 mapped at ffff6000
> ACPI table found: RSDT v1 [PTLTD RSDT 1540.0]
> __va_range(0x3fefbe78, 0x24): idx=8 mapped at ffff6000
> __va_range(0x3fefbe78, 0x74): idx=8 mapped at ffff6000
> ACPI table found: FACP v1 [INTEL K_CANYON 1540.0]
> __va_range(0x3fefbeec, 0x24): idx=8 mapped at ffff6000
> __va_range(0x3fefbeec, 0x9c): idx=8 mapped at ffff6000
> ACPI table found: APIC v1 [PTLTD APIC 1540.0]
> __va_range(0x3fefbeec, 0x9c): idx=8 mapped at ffff6000
> LAPIC (acpi_id[0x0000] id[0x0] enabled[1])
> CPU 0 (0x0000) enabledProcessor #0 Pentium 4(tm) XEON(tm) APIC version 16
>
> LAPIC (acpi_id[0x0001] id[0x6] enabled[1])
> CPU 1 (0x0600) enabledProcessor #6 Pentium 4(tm) XEON(tm) APIC version 16
>
> LAPIC (acpi_id[0x0002] id[0x1] enabled[1])
> CPU 2 (0x0100) enabledProcessor #1 Pentium 4(tm) XEON(tm) APIC version 16
>
> LAPIC (acpi_id[0x0003] id[0x7] enabled[1])
> CPU 3 (0x0700) enabledProcessor #7 Pentium 4(tm) XEON(tm) APIC version 16
>
> IOAPIC (id[0x2] address[0xfec00000] global_irq_base[0x0])
> IOAPIC (id[0x3] address[0xfec80000] global_irq_base[0x18])
> IOAPIC (id[0x4] address[0xfec80400] global_irq_base[0x30])
> INT_SRC_OVR (bus[0] irq[0x0] global_irq[0x2] polarity[0x1] trigger[0x1])
> INT_SRC_OVR (bus[0] irq[0x9] global_irq[0x9] polarity[0x1] trigger[0x3])
> LAPIC_NMI (acpi_id[0x0000] polarity[0x1] trigger[0x1] lint[0x1])
> LAPIC_NMI (acpi_id[0x0001] polarity[0x1] trigger[0x1] lint[0x1])
> LAPIC_NMI (acpi_id[0x0002] polarity[0x1] trigger[0x1] lint[0x1])
> LAPIC_NMI (acpi_id[0x0003] polarity[0x1] trigger[0x1] lint[0x1])
> 4 CPUs total
> Local APIC address fee00000
> __va_range(0x3fefbf88, 0x24): idx=8 mapped at ffff6000
> __va_range(0x3fefbf88, 0x28): idx=8 mapped at ffff6000
> ACPI table found: BOOT v1 [PTLTD $SBFTBL$ 1540.0]
> __va_range(0x3fefbfb0, 0x24): idx=8 mapped at ffff6000
> __va_range(0x3fefbfb0, 0x50): idx=8 mapped at ffff6000
> ACPI table found: SPCR v1 [PTLTD $UCRTBL$ 1540.0]
> Enabling the CPU's according to the ACPI table
> Intel MultiProcessor Specification v1.4
> Virtual Wire compatibility mode.
> OEM ID: Product ID: Kings Canyon APIC at: 0xFEE00000
> I/O APIC #2 Version 32 at 0xFEC00000.
> I/O APIC #3 Version 32 at 0xFEC80000.
> I/O APIC #4 Version 32 at 0xFEC80400.
> Processors: 4
> Kernel command line: ro root=LABEL=/ console=ttyS0,9600n8 nmi_watchdog=1
> [snip]
>
>
> However, when I boot the machine with the "noht" option the ACPI table
> search is skipped, _but_ it still finds 4 processors in the MP table :
>
> Linux version 2.4.20-rc2 (root@puma1.office.scali.no) (gcc version 3.2 20020903 (Red Hat Linux 8.0 3.2-7)) #4 SMP Sat Nov 16 14:06:13 CET 2002
> BIOS-provided physical RAM map:
> BIOS-e820: 0000000000000000 - 000000000009f400 (usable)
> BIOS-e820: 000000000009f400 - 00000000000a0000 (reserved)
> BIOS-e820: 00000000000d8000 - 00000000000e0000 (reserved)
> BIOS-e820: 00000000000e4000 - 0000000000100000 (reserved)
> BIOS-e820: 0000000000100000 - 000000003fef0000 (usable)
> BIOS-e820: 000000003fef0000 - 000000003fefc000 (ACPI data)
> BIOS-e820: 000000003fefc000 - 000000003ff00000 (ACPI NVS)
> BIOS-e820: 000000003ff00000 - 000000003ff80000 (usable)
> BIOS-e820: 000000003ff80000 - 0000000040000000 (reserved)
> BIOS-e820: 00000000fec00000 - 00000000fec10000 (reserved)
> BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
> BIOS-e820: 00000000ff800000 - 00000000ffc00000 (reserved)
> BIOS-e820: 00000000fff00000 - 0000000100000000 (reserved)
> 127MB HIGHMEM available.
> 896MB LOWMEM available.
> found SMP MP-table at 000f7030
> hm, page 000f7000 reserved twice.
> hm, page 000f8000 reserved twice.
> hm, page 0009f000 reserved twice.
> hm, page 000a0000 reserved twice.
> On node 0 totalpages: 262016
> zone(0): 4096 pages.
> zone(1): 225280 pages.
> zone(2): 32640 pages.
> Intel MultiProcessor Specification v1.4
> Virtual Wire compatibility mode.
> OEM ID: Product ID: Kings Canyon APIC at: 0xFEE00000
> Processor #0 Pentium 4(tm) XEON(tm) APIC version 20
> Processor #6 Pentium 4(tm) XEON(tm) APIC version 20
> Processor #1 Pentium 4(tm) XEON(tm) APIC version 20
> Processor #7 Pentium 4(tm) XEON(tm) APIC version 20
> I/O APIC #2 Version 32 at 0xFEC00000.
> I/O APIC #3 Version 32 at 0xFEC80000.
> I/O APIC #4 Version 32 at 0xFEC80400.
> Processors: 4
> Kernel command line: ro root=LABEL=/ console=ttyS0,9600n8 nmi_watchdog=1 noht
>
> Since the HT feature is enabled in the BIOS it seems normal to me that 4
> processors are reported both in the MP table and in the ACPI table.
> Shouldn't the 'noht' option handle this ?
>
> I have two of these machines and can assist in testing out patches etc.

I know too little to comment definitively, but it's my understanding
that a dual HT machine should only show 2 processors in its MP table,
their siblings only appearing through analysis of the ACPI tables.

Whether it's that your MP table has been wrongly set up, or that
you've really been given 4 processors when you only asked for 2
(sue your supplier!), I cannot say. I've copied Jun at Intel
and Arjan at RedHat, and hope they can shed more light on this.

Hugh

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