linux-kernel - Re: [PATCH] x86/jailhouse: fix building without X86

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Date:   Tue, 16 Jan 2018 10:34:42 +0800
From:   Dou Liyang <douly.fnst@...fujitsu.com>
To:     Arnd Bergmann <arnd@...db.de>, Jan Kiszka <jan.kiszka@...mens.com>,
        Thomas Gleixner <tglx@...utronix.de>, <x86@...nel.org>
CC:     <jailhouse-dev@...glegroups.com>, Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Juergen Gross <jgross@...e.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/jailhouse: fix building without X86_X2APIC

Hi Arnd,

At 01/16/2018 09:25 AM, Dou Liyang wrote:
> Hi Arnd,
> 
> At 01/16/2018 04:23 AM, Arnd Bergmann wrote:
>> When CONFIG_X86_X2APIC is disabled, jailhouse fails to build:
>>
>> arch/x86/kernel/jailhouse.c: In function 'jailhouse_get_smp_config':
>> arch/x86/kernel/jailhouse.c:73:3: error: 'x2apic_phys' undeclared 
>> (first use in this function); did you mean 'x2apic_mode'?
>>
>> The code is protected by an appropriate x2apic_enabled() check that leads
>> to the assignment being optimized out without a link-time reference to
>> x2apic_phys, so we just lack a declaration.
>>
>> Let's move x2apic_mode and x2apic_phys outside of the #ifdef together,
>> for consistency.
>>
>> Fixes: 11c8dc419bbc ("x86/jailhouse: Enable APIC and SMP support")
>> Signed-off-by: Arnd Bergmann <arnd@...db.de>
>> ---
>>   arch/x86/include/asm/apic.h | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
>> index 98722773391d..0317d635d9ba 100644
>> --- a/arch/x86/include/asm/apic.h
>> +++ b/arch/x86/include/asm/apic.h
>> @@ -188,6 +188,8 @@ static inline void 
>> lapic_assign_system_vectors(void) { }
>>   static inline void lapic_assign_legacy_vector(unsigned int i, bool 
>> r) { }
>>   #endif /* !CONFIG_X86_LOCAL_APIC */
>> +extern int x2apic_mode;
>> +extern int x2apic_phys;
> We can't do that, adding a macro for the X2APIC=n case is enough
> 
I am sorry when I looked into your code in tip tree. I found this
measure is not true. please try the the following v2 patch.

The reason I don't want to expose the x2apic_mode and x2apic_phys is
that they may be misused in X2APIC=n case. So I create an interface to
wrap it. do you think so? ;-)

Thanks,
	dou.
---
  arch/x86/include/asm/apic.h | 10 +++++++++-
  arch/x86/kernel/apic/apic.c |  2 +-
  arch/x86/kernel/jailhouse.c |  2 +-
  3 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 98722773391d..ac25ac2e49af 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -251,6 +251,11 @@ static inline u64 native_x2apic_icr_read(void)

  extern int x2apic_mode;
  extern int x2apic_phys;
+static inline void apic_set_x2apic_phys(void)
+{
+	x2apic_phys = 1;
+}
+
  extern void __init check_x2apic(void);
  extern void x2apic_setup(void);
  static inline int x2apic_enabled(void)
@@ -265,7 +270,10 @@ static inline void x2apic_setup(void) { }
  static inline int x2apic_enabled(void) { return 0; }

  #define x2apic_mode		(0)
-#define	x2apic_supported()	(0)
+#define x2apic_phys		(0)
+#define x2apic_supported()	(0)
+
+static inline void apic_set_x2apic_phys(void){}
  #endif /* !CONFIG_X86_X2APIC */

  struct irq_data;
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 25ddf02598d2..440ff200104f 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1746,7 +1746,7 @@ static __init void try_to_enable_x2apic(int 
remap_mode)
  		 * without IR all CPUs can be addressed by IOAPIC/MSI
  		 * only in physical mode
  		 */
-		x2apic_phys = 1;
+		apic_set_x2apic_phys();
  	}
  	x2apic_enable();
  }
diff --git a/arch/x86/kernel/jailhouse.c b/arch/x86/kernel/jailhouse.c
index d6d5976a9b51..ce62162efcf2 100644
--- a/arch/x86/kernel/jailhouse.c
+++ b/arch/x86/kernel/jailhouse.c
@@ -70,7 +70,7 @@ static void __init jailhouse_get_smp_config(unsigned 
int early)
  		 * We do not have access to IR inside Jailhouse non-root cells.
  		 * So we have to run in physical mode.
  		 */
-		x2apic_phys = 1;
+		apic_set_x2apic_phys();

  		/*
  		 * This will trigger the switch to apic_x2apic_phys.
-- 
> Thanks,
>      dou
> 
> -------------------------8<----------------------
> 
> Subject: [PATCH] x86/apic: Add a macro named x2apic_phys for the 
> X2APIC=n case
> 
> The x86 system may build failed in the X2APIC=n case, due to the missing of
> x2apic_phys.
> 
> So add a macro named x2apic_phys for the X2APIC=n case.
> 
> Signed-off-by: Dou Liyang <douly.fnst@...fujitsu.com>
> ---
>   arch/x86/include/asm/apic.h | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
> index a9e57f08bfa6..ca5940fb995a 100644
> --- a/arch/x86/include/asm/apic.h
> +++ b/arch/x86/include/asm/apic.h
> @@ -264,7 +264,8 @@ static inline void x2apic_setup(void) { }
>   static inline int x2apic_enabled(void) { return 0; }
> 
>   #define x2apic_mode        (0)
> -#define    x2apic_supported()    (0)
> +#define x2apic_phys        (0)
> +#define x2apic_supported()    (0)
>   #endif /* !CONFIG_X86_X2APIC */
> 
>   struct irq_data;