Re: [tip:x86/urgent] x86: Detect use of extended APIC ID for AMD CPUs

Yinghai Lu
2009-06-07T18:47:51Z

tip-bot for Andreas Herrmann wrote:
> Commit-ID: 37f36c1017f0032fa7a1fb85a0cddfc0d526d17f
> Gitweb: http://git.kernel.org/tip/37f36c1017f0032fa7a1fb85a0cddfc0d526d17f
> Author: Andreas Herrmann <andreas.herrmann3@amd.com>
> AuthorDate: Thu, 4 Jun 2009 12:40:16 +0200
> Committer: Ingo Molnar <mingo@elte.hu>
> CommitDate: Sun, 7 Jun 2009 16:39:38 +0200
>
> x86: Detect use of extended APIC ID for AMD CPUs
>
> Booting a 32-bit kernel on Magny-Cours results in the following panic
>
> ...
> Using APIC driver default
> ...
> Overriding APIC driver with bigsmp
> ...
> Getting VERSION: 80050010
> Getting VERSION: 80050010
> Getting ID: 10000000
> Getting ID: ef000000
> Getting LVT0: 700
> Getting LVT1: 10000
> Kernel panic - not syncing: Boot APIC ID in local APIC unexpected (16 vs 0)
> Pid: 1, comm: swapper Not tainted 2.6.30-rcX #2
> Call Trace:
> [<c05194da>] ? panic+0x38/0xd3
> [<c0743102>] ? native_smp_prepare_cpus+0x259/0x31f
> [<c073b19d>] ? kernel_init+0x3e/0x141
> [<c073b15f>] ? kernel_init+0x0/0x141
> [<c020325f>] ? kernel_thread_helper+0x7/0x10
>
> The reason is that default_get_apic_id handled extension of local APIC
> ID field just in case of XAPIC.
>
> Thus for this AMD CPU, default_get_apic_id() returns 0 and
> bigsmp_get_apic_id() returns 16 which leads to the respective kernel
> panic.
>
> This patch introduces a Linux specific feature flag to indicate
> support for extended APIC id (8 bits instead of 4 bits width) and sets
> the flag on AMD CPUs if applicable.
>
> Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
> Cc: <stable@kernel.org>
> LKML-Reference: <20090604104016.GT5736@alberich.amd.com>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
>
>
> ---
> arch/x86/include/asm/apic.h | 2 +-
> arch/x86/include/asm/cpufeature.h | 1 +
> arch/x86/kernel/cpu/amd.c | 10 ++++++++++
> 3 files changed, 12 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
> index 42f2f83..9b2c049 100644
> --- a/arch/x86/include/asm/apic.h
> +++ b/arch/x86/include/asm/apic.h
> @@ -410,7 +410,7 @@ static inline unsigned default_get_apic_id(unsigned long x)
> {
> unsigned int ver = GET_APIC_VERSION(apic_read(APIC_LVR));
>
> - if (APIC_XAPIC(ver))
> + if (APIC_XAPIC(ver) || boot_cpu_has(X86_FEATURE_EXTD_APICID))
> return (x >> 24) & 0xFF;
> else
> return (x >> 24) & 0x0F;

looks like we should fix APIC_XAPIC() or have one global apic_ver.

YH