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SubjectRe: [LKP] [x86] 811565123a: BUG: kernel hang in early-boot stage, last printk: Probing EDD (edd=off to disable)... ok
On Fri, Oct 14, 2016 at 12:56:00PM +0800, Ye Xiaolong wrote:
> On 10/14, Ye Xiaolong wrote:
> >On 10/13, Andi Kleen wrote:
> >>Andi Kleen <andi@firstfloor.org> writes:
> >>
> >>Any comments on this?
> >>
> >>I still cannot reproduce the failure unfortunately.
> >>
> >
> >Btw, you can try below commands to reproduce the error on your local
> >host, they will download the necessary images and run QEMU:
> >
> > git clone git://git.kernel.org/pub/scm/linux/kernel/git/wfg/lkp-tests.git
> > cd lkp-tests
> > bin/lkp qemu -k KERNEL job-script # job-script is attached in the original report email
>
> Results show this hang may be related to gcc version, with gcc version
> 4.8.4 (Ubuntu 4.8.4-2ubuntu1~14.04.3), kernel could boot without early
> hang, but if kernel was built with gcc version 6.2.0 20160901 (Debian
> 6.2.0-3), it will stuck in the early stage:

I built a mainline gcc 6.2, unfortunately still doesn't reproduce. The kernel
with your config boots to root.

My guess is that something is broken with paravirt ops on 32bit
on that compiler.

I created a new patch with the probing code moved to a separate
function. Can you test if that works?

-Andi


commit 65c92de6678f04ce14b237d7073e164b98d9a8be
Author: Andi Kleen <ak@linux.intel.com>
Date: Wed May 4 06:07:44 2016 -0700

x86: Report Intel platform_id in /proc/cpuinfo

We have a need to distinguish systems based on their platform ID.
For example this is useful to distinguish systems with L4 cache
versus ones without.

There is a 3 bit identifier (also called processor flags) in
the IA32_PLATFORM_ID MSR that can give a more fine grained
identification of the CPU than just the model number/stepping.

IA32_PLATFORM_ID is architectural.

The MSR can be also accessed through /dev/cpu/*/msr, but that
requires root and is awkward.

The patch moves the reading of PLATFORM_INFO from the
(late) microcode driver code into the main intel CPU initialization
path and then also prints it in /proc/cpuinfo

v2: Handle 0 platform_id. Fix commit message.
v3: Move some code to cpu/intel.c
v4: Update description too.
v5: Move msr probe code out of line to w/a potential gcc 6 bug
Cc: hmh@hmh.eng.br
Signed-off-by: Andi Kleen <ak@linux.intel.com>

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 63def9537a2d..c1313b3f3e59 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -135,6 +135,8 @@ struct cpuinfo_x86 {
/* Index into per_cpu list: */
u16 cpu_index;
u32 microcode;
+ u32 platform_id;
+ u8 has_platform_id;
};

#define X86_VENDOR_INTEL 0
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index fcd484d2bb03..7da7f008cee0 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -61,6 +61,19 @@ void check_mpx_erratum(struct cpuinfo_x86 *c)
}
}

+/* noinline to work around problem with gcc 6.2 */
+static noinline void probe_platformid(struct cpuinfo_x86 *c)
+{
+ if ((c->x86_model >= 5) || (c->x86 > 6)) {
+ unsigned val[2];
+
+ /* get processor flags from MSR 0x17 */
+ rdmsr(MSR_IA32_PLATFORM_ID, val[0], val[1]);
+ c->platform_id = (val[1] >> 18) & 7;
+ c->has_platform_id = true;
+ }
+}
+
static void early_init_intel(struct cpuinfo_x86 *c)
{
u64 misc_enable;
@@ -211,6 +224,8 @@ static void early_init_intel(struct cpuinfo_x86 *c)
}

check_mpx_erratum(c);
+
+ probe_platformid(c);
}

#ifdef CONFIG_X86_32
diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index cdc0deab00c9..fab07e49192e 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -855,17 +855,13 @@ static int collect_cpu_info(int cpu_num, struct cpu_signature *csig)
{
static struct cpu_signature prev;
struct cpuinfo_x86 *c = &cpu_data(cpu_num);
- unsigned int val[2];

memset(csig, 0, sizeof(*csig));

csig->sig = cpuid_eax(0x00000001);

- if ((c->x86_model >= 5) || (c->x86 > 6)) {
- /* get processor flags from MSR 0x17 */
- rdmsr(MSR_IA32_PLATFORM_ID, val[0], val[1]);
- csig->pf = 1 << ((val[1] >> 18) & 7);
- }
+ if (c->has_platform_id)
+ csig->pf = 1 << c->platform_id;

csig->rev = c->microcode;

diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
index 18ca99f2798b..5345d50ed709 100644
--- a/arch/x86/kernel/cpu/proc.c
+++ b/arch/x86/kernel/cpu/proc.c
@@ -76,6 +76,8 @@ static int show_cpuinfo(struct seq_file *m, void *v)
seq_puts(m, "stepping\t: unknown\n");
if (c->microcode)
seq_printf(m, "microcode\t: 0x%x\n", c->microcode);
+ if (c->has_platform_id)
+ seq_printf(m, "platform_id\t: %d\n", c->platform_id);

if (cpu_has(c, X86_FEATURE_TSC)) {
unsigned int freq = cpufreq_quick_get(cpu);
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