linux-kernel - Re: [PATCH 2/4] kvm: x86: allow set apic and ioapic debug dynamically

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Date:   Wed, 3 Jul 2019 19:27:47 +0300
From:   Liran Alon <liran.alon@...cle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Yi Wang <wang.yi59@....com.cn>, rkrcmar@...hat.com,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        xue.zhihong@....com.cn, up2wing@...il.com, wang.liang82@....com.cn
Subject: Re: [PATCH 2/4] kvm: x86: allow set apic and ioapic debug dynamically



> On 3 Jul 2019, at 19:23, Paolo Bonzini <pbonzini@...hat.com> wrote:
> 
> On 01/07/19 08:21, Yi Wang wrote:
>> There are two *_debug() macros in kvm apic source file:
>> - ioapic_debug, which is disable using #if 0
>> - apic_debug, which is commented
>> 
>> Maybe it's better to control these two macros using CONFIG_KVM_DEBUG,
>> which can be set in make menuconfig.
>> 
>> Signed-off-by: Yi Wang <wang.yi59@....com.cn>
>> ---
>> arch/x86/kvm/ioapic.c | 2 +-
>> arch/x86/kvm/lapic.c  | 5 ++++-
>> 2 files changed, 5 insertions(+), 2 deletions(-)
>> 
>> diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
>> index 1add1bc..8099253 100644
>> --- a/arch/x86/kvm/ioapic.c
>> +++ b/arch/x86/kvm/ioapic.c
>> @@ -45,7 +45,7 @@
>> #include "lapic.h"
>> #include "irq.h"
>> 
>> -#if 0
>> +#ifdef CONFIG_KVM_DEBUG
>> #define ioapic_debug(fmt,arg...) printk(KERN_WARNING fmt,##arg)
>> #else
>> #define ioapic_debug(fmt, arg...)
>> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
>> index 4924f83..dfff5c6 100644
>> --- a/arch/x86/kvm/lapic.c
>> +++ b/arch/x86/kvm/lapic.c
>> @@ -54,8 +54,11 @@
>> #define PRIu64 "u"
>> #define PRIo64 "o"
>> 
>> -/* #define apic_debug(fmt,arg...) printk(KERN_WARNING fmt,##arg) */
>> +#ifdef CONFIG_KVM_DEBUG
>> +#define apic_debug(fmt,arg...) printk(KERN_WARNING fmt,##arg)
>> +#else
>> #define apic_debug(fmt, arg...) do {} while (0)
>> +#endif
>> 
>> /* 14 is the version for Xeon and Pentium 8.4.8*/
>> #define APIC_VERSION			(0x14UL | ((KVM_APIC_LVT_NUM - 1) << 16))
>> 
> 
> I would just drop all of them.  I've never used them in years, the kvm
> tracepoints are enough.
> 
> Paolo

As someone who have done many LAPIC/IOAPIC debugging, I tend to agree. :)

-Liran