Re: port-i386/52266: Double fault early in boot with AMD Am5x86 CPU

["John D. Baker" <jdbaker%mylinuxisp.com@localhost>]

The following reply was made to PR port-i386/52266; it has been noted by GNATS.

From: "John D. Baker" <jdbaker%mylinuxisp.com@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: port-i386/52266: Double fault early in boot with AMD Am5x86 CPU
Date: Tue, 11 Jul 2017 10:48:54 -0500 (CDT)

 On Tue, 11 Jul 2017 18:12:37 +0900, Kimihiro Nonaka <nonakap%gmail.com@localhost>
 wrote:
 
 > On 2017-07-09 14:45 GMT+09:00 John D. Baker <jdbaker%mylinuxisp.com@localhost>:
 > 
 > >  Just to double check, I grabbed:
 > >
 > >    http://nycdn.netbsd.org/pub/NetBSD-daily/HEAD/201707082110Z/i386/binary/kernel/netbsd-GENERIC.gz
 > >
 > >  and it panics on the net4501 the same as my locally-built kernels:
 > 
 > Could you try the following patch?
 > 
 > diff --git a/sys/arch/x86/x86/lapic.c b/sys/arch/x86/x86/lapic.c
 > index 415bb65b4e5..f87de042054 100644
 > --- a/sys/arch/x86/x86/lapic.c
 > +++ b/sys/arch/x86/x86/lapic.c
 > @@ -237,7 +237,8 @@ lapic_is_x2apic(void)
 >  {
 >      uint64_t msr;
 > 
 > -    if (rdmsr_safe(MSR_APICBASE, &msr) == EFAULT)
 > +    if (!ISSET(cpu_feature[0], CPUID_MSR) ||
 > +        rdmsr_safe(MSR_APICBASE, &msr) == EFAULT)
 >          return false;
 >      return (msr & (APICBASE_EN | APICBASE_EXTD)) ==
 >          (APICBASE_EN | APICBASE_EXTD);
 
 With the above patch, my net4501 boots -current (8.99.1) again!
 
 Thanks for the patch.  Please commit and pull up to netbsd-8!
 
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