On Sun, Jun 7, 2009 at 7:24 AM, tip-bot for Cyrill Gorcunov<gorcunov@xxxxxxxxxx> wrote: > Commit-ID: 103428e57be323c3c5545db8ad12667099bc6005 > Gitweb: http://git.kernel.org/tip/103428e57be323c3c5545db8ad12667099bc6005 > Author: Cyrill Gorcunov <gorcunov@xxxxxxxxxx> > AuthorDate: Sun, 7 Jun 2009 16:48:40 +0400 > Committer: Ingo Molnar <mingo@xxxxxxx> > CommitDate: Sun, 7 Jun 2009 16:08:05 +0200 > > x86, apic: Fix dummy apic read operation together with broken MP handling > > Ingo Molnar reported that read_apic is buggy novadays: > > [ 0.000000] Using APIC driver default > [ 0.000000] SMP: Allowing 1 CPUs, 0 hotplug CPUs > [ 0.000000] Local APIC disabled by BIOS -- you can enable it with "lapic" > [ 0.000000] APIC: disable apic facility > [ 0.000000] ------------[ cut here ]------------ > [ 0.000000] WARNING: at arch/x86/kernel/apic/apic.c:254 native_apic_read_dummy+0x2d/0x3b() > [ 0.000000] Hardware name: HP OmniBook PC > > Indeed we still rely on apic->read operation for SMP compiled > kernel. And instead of disfigure the SMP code with #ifdef we > allow to call apic->read. To capture any unexpected results > we check for apic->read being called for sane reason via > WARN_ON_ONCE but(!) instead of OR we should use AND logical > operation (thanks Yinghai for spotting the root of the problem). > > Along with that we could be have bad MP table and we are > to fix it that way no SMP started and no complains about > BIOS bug if apic was just disabled via command line. > > Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx> > Cc: Yinghai Lu <yinghai@xxxxxxxxxx> > LKML-Reference: <20090607124840.GD4547@lenovo> > Signed-off-by: Ingo Molnar <mingo@xxxxxxx> > > > --- > arch/x86/kernel/apic/apic.c | 9 ++++++++- > arch/x86/kernel/smpboot.c | 8 +++++--- > 2 files changed, 13 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c > index e82488d..a4c9cf0 100644 > --- a/arch/x86/kernel/apic/apic.c > +++ b/arch/x86/kernel/apic/apic.c > @@ -249,7 +249,7 @@ static void native_apic_write_dummy(u32 reg, u32 v) > > static u32 native_apic_read_dummy(u32 reg) > { > - WARN_ON_ONCE((cpu_has_apic || !disable_apic)); > + WARN_ON_ONCE((cpu_has_apic && !disable_apic)); > return 0; > } > > @@ -1609,6 +1609,13 @@ void __init init_apic_mappings(void) > new_apicid = read_apic_id(); > if (boot_cpu_physical_apicid != new_apicid) { > boot_cpu_physical_apicid = new_apicid; > + /* > + * yeah -- we lie about apic_version > + * in case if apic was disabled via boot option > + * but it's not a problem for SMP compiled kernel > + * since smp_sanity_check is prepared for such a case > + * and disable smp mode > + */ > apic_version[new_apicid] = > GET_APIC_VERSION(apic_read(APIC_LVR)); > } > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c > index d2e8de9..7c80007 100644 > --- a/arch/x86/kernel/smpboot.c > +++ b/arch/x86/kernel/smpboot.c > @@ -992,10 +992,12 @@ static int __init smp_sanity_check(unsigned max_cpus) > */ > if (APIC_INTEGRATED(apic_version[boot_cpu_physical_apicid]) && > !cpu_has_apic) { > - printk(KERN_ERR "BIOS bug, local APIC #%d not detected!...\n", > - boot_cpu_physical_apicid); > - printk(KERN_ERR "... forcing use of dummy APIC emulation." > + if (!disable_apic) { > + pr_err("BIOS bug, local APIC #%d not detected!...\n", > + boot_cpu_physical_apicid); > + pr_err("... forcing use of dummy APIC emulation." > "(tell your hw vendor)\n"); > + } It seems we don't need this check here. when we have disable_apic, cpu_has_apic is cleared forcely. YH -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html