Subject: Re: linux-next: build failure after merge of the final tree (xen tree related)

From: Jeremy Fitzhardinge <[email-masked]>
Date: Mon, 26 Jul 2010 10:25:25 -0700

On 07/26/2010 03:43 AM, Stefano Stabellini wrote:
> On Mon, 26 Jul 2010, Stephen Rothwell wrote:
>> Hi all,
>>
>> After merging the final tree, today's linux-next build (i386 defconfig)
>> failed like this:
>>
>> arch/x86/built-in.o: In function `init_hypervisor_platform':
>> (.init.text+0x3ca4): undefined reference to `x86_hyper_xen_hvm'
>> arch/x86/built-in.o: In function `init_hypervisor_platform':
>> (.init.text+0x3cad): undefined reference to `x86_hyper_xen_hvm'
>>
>> Caused by commit bee6ab53e652a414af20392899879b58cd80d033 ("x86: early PV
>> on HVM features initialization").
>>
>> I reverted commit 4b9100d12d15c0eaf23d9edc86228e1bdf452dc2 ("Merge branch
>> 'upstream/pvhvm' into upstream/xen") for today (since there were
>> dependencies on the above commit).
> The problem is that x86_hyper_xen_hvm is in arch/x86/xen/enlighten.c,
> that is compiled only when CONFIG_XEN is enabled.
> The appended patch fixes the issue moving x86_hyper_xen_hvm to
> arch/x86/kernel/cpu/xen.c that is always compiled.
>
> An shorter alternative solution would be just to ifdef CONFIG_XEN
> x86_hyper_xen_hvm in arch/x86/kernel/cpu/hypervisor.c.

Seems like the most sensible thing to do.  What's the point in detecting 
Xen if we don't have CONFIG_XEN enabled?

     J

>
> Signed-off-by: Stefano Stabellini<[email-masked]>
>
> ---
>
> diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
> index 5e3a351..25d2e82 100644
> --- a/arch/x86/kernel/cpu/Makefile
> +++ b/arch/x86/kernel/cpu/Makefile
> @@ -15,6 +15,7 @@ CFLAGS_common.o		:= $(nostackp)
>   obj-y			:= intel_cacheinfo.o scattered.o topology.o
>   obj-y			+= proc.o capflags.o powerflags.o common.o
>   obj-y			+= vmware.o hypervisor.o sched.o mshyperv.o
> +obj-y			+= xen.o
>
>   obj-$(CONFIG_X86_32)	+= bugs.o cmpxchg.o
>   obj-$(CONFIG_X86_64)	+= bugs_64.o
> diff --git a/arch/x86/kernel/cpu/xen.c b/arch/x86/kernel/cpu/xen.c
> new file mode 100644
> index 0000000..b879de5
> --- /dev/null
> +++ b/arch/x86/kernel/cpu/xen.c
> @@ -0,0 +1,68 @@
> +/*
> + * Copyright (C) 2010, Citrix Systems
> + * Author : Stefano Stabellini<[email-masked]>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful, but
> + * WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
> + * NON INFRINGEMENT.  See the GNU General Public License for more
> + * details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
> + *
> + */
> +
> +#include<linux/init.h>
> +#include<asm/x86_init.h>
> +#include<asm/hypervisor.h>
> +#include<asm/processor.h>
> +#include<xen/xen.h>
> +
> +uint32_t xen_cpuid_base(void)
> +{
> +	uint32_t base, eax, ebx, ecx, edx;
> +	char signature[13];
> +
> +	for (base = 0x40000000; base<  0x40010000; base += 0x100) {
> +		cpuid(base,&eax,&ebx,&ecx,&edx);
> +		*(uint32_t *)(signature + 0) = ebx;
> +		*(uint32_t *)(signature + 4) = ecx;
> +		*(uint32_t *)(signature + 8) = edx;
> +		signature[12] = 0;
> +
> +		if (!strcmp("XenVMMXenVMM", signature)&&  ((eax - base)>= 2))
> +			return base;
> +	}
> +
> +	return 0;
> +}
> +
> +static void __init __xen_hvm_guest_init(void)
> +{
> +	xen_hvm_guest_init();
> +}
> +
> +static bool __init xen_hvm_platform(void)
> +{
> +	if (xen_pv_domain())
> +		return false;
> +
> +	if (!xen_cpuid_base())
> +		return false;
> +
> +	return true;
> +}
> +
> +const __refconst struct hypervisor_x86 x86_hyper_xen_hvm = {
> +	.name			= "Xen HVM",
> +	.detect			= xen_hvm_platform,
> +	.init_platform		= __xen_hvm_guest_init,
> +};
> +EXPORT_SYMBOL(x86_hyper_xen_hvm);
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 75b479a..06f954d 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1205,25 +1205,6 @@ asmlinkage void __init xen_start_kernel(void)
>   #endif
>   }
>
> -static uint32_t xen_cpuid_base(void)
> -{
> -	uint32_t base, eax, ebx, ecx, edx;
> -	char signature[13];
> -
> -	for (base = 0x40000000; base<  0x40010000; base += 0x100) {
> -		cpuid(base,&eax,&ebx,&ecx,&edx);
> -		*(uint32_t *)(signature + 0) = ebx;
> -		*(uint32_t *)(signature + 4) = ecx;
> -		*(uint32_t *)(signature + 8) = edx;
> -		signature[12] = 0;
> -
> -		if (!strcmp("XenVMMXenVMM", signature)&&  ((eax - base)>= 2))
> -			return base;
> -	}
> -
> -	return 0;
> -}
> -
>   static int init_hvm_pv_info(int *major, int *minor)
>   {
>   	uint32_t eax, ebx, ecx, edx, pages, msr, base;
> @@ -1300,7 +1281,7 @@ static struct notifier_block __cpuinitdata xen_hvm_cpu_notifier = {
>   	.notifier_call	= xen_hvm_cpu_notify,
>   };
>
> -static void __init xen_hvm_guest_init(void)
> +void __init xen_hvm_guest_init(void)
>   {
>   	int r;
>   	int major, minor;
> @@ -1320,21 +1301,3 @@ static void __init xen_hvm_guest_init(void)
>   	xen_hvm_init_time_ops();
>   	xen_hvm_init_mmu_ops();
>   }
> -
> -static bool __init xen_hvm_platform(void)
> -{
> -	if (xen_pv_domain())
> -		return false;
> -
> -	if (!xen_cpuid_base())
> -		return false;
> -
> -	return true;
> -}
> -
> -const __refconst struct hypervisor_x86 x86_hyper_xen_hvm = {
> -	.name			= "Xen HVM",
> -	.detect			= xen_hvm_platform,
> -	.init_platform		= xen_hvm_guest_init,
> -};
> -EXPORT_SYMBOL(x86_hyper_xen_hvm);
> diff --git a/include/xen/xen.h b/include/xen/xen.h
> index a164024..dfc2784 100644
> --- a/include/xen/xen.h
> +++ b/include/xen/xen.h
> @@ -9,9 +9,12 @@ enum xen_domain_type {
>
>   #ifdef CONFIG_XEN
>   extern enum xen_domain_type xen_domain_type;
> +extern void __init xen_hvm_guest_init(void);
>   #else
>   #define xen_domain_type		XEN_NATIVE
> +#define xen_hvm_guest_init() do { } while (0)
>   #endif
> +extern uint32_t xen_cpuid_base(void);
>
>   #define xen_domain()		(xen_domain_type != XEN_NATIVE)
>   #define xen_pv_domain()		(xen_domain()&&			\
>