linux-kernel - Re: Current kernel fails to compile with KVM on PowerPC

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Date:	Mon, 27 Feb 2012 01:30:59 +0100
From:	Alexander Graf <agraf@...e.de>
To:	Jörg Sommer <joerg@...a.gnuu.de>
Cc:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	kvm list <kvm@...r.kernel.org>, kvm-ppc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Current kernel fails to compile with KVM on PowerPC


On 27.02.2012, at 01:08, Jörg Sommer wrote:

> Alexander Graf hat am Sun 26. Feb, 12:43 (+0100) geschrieben:
>> On 25.02.2012, at 15:51, Jörg Sommer wrote:
>>> Jörg Sommer hat am Tue 21. Feb, 09:32 (+0100) geschrieben:
>>>> Alexander Graf hat am Mon 20. Feb, 22:27 (+0100) geschrieben:
>>>>> On 20.02.2012, at 18:38, Jörg Sommer wrote:
>>>>>> Alexander Graf hat am Tue 22. Nov, 22:29 (+0100) geschrieben:
>>>>>>> On 22.11.2011, at 21:04, Jörg Sommer wrote:
>>>>>>>> [1] »kernel BUG at include/linux/kvm_host.h:603!«
>>>>>>>> http://www.mail-archive.com/kvm@vger.kernel.org/msg61433.html
>>>>>>> 
>>>>>>> This is unfortunately still there. It's because of preemption being
>>>>>>> enabled. Please just use CONFIG_PREEMPT_NONE for the time being
>>>>>> 
>>>>>> This doesn't help. I've build with CONFIG_PREEMPT_NONE, but I'm getting
>>>>>> this Oops, when I start qemu.
>>>>> 
>>>>> Could you please try git://git.kernel.org/pub/scm/virt/kvm/kvm.git? I
>>>>> fixed a bunch of things with preemption since then and it definitely
>>>>> worked for me. If it still fails in that tree, I can try again to
>>>>> reproduce it :).
>>>> 
>>>> This kernel (e9badff4b38a3f8b2c20aa8a30db210caf85a497) fails to build:
>>>> 
>>>> CC [M]  arch/powerpc/kvm/book3s_pr.o
>>>> arch/powerpc/kvm/book3s_pr.c: In function ‘kvm_vcpu_ioctl_get_one_reg’:
>>>> arch/powerpc/kvm/book3s_pr.c:883:45: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
>>>> arch/powerpc/kvm/book3s_pr.c:883:80: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
> 
>> Yikes. Does this patch work for you?
> 
>> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
>> index ee222ec..f329eae 100644
>> --- a/arch/powerpc/kvm/book3s_pr.c
>> +++ b/arch/powerpc/kvm/book3s_pr.c
>> @@ -880,7 +880,8 @@ int kvm_vcpu_ioctl_get_one_reg(struct kvm_vcpu *vcpu, struct kvm_one_reg *reg)
>> 
>>        switch (reg->id) {
>>        case KVM_REG_PPC_HIOR:
>> -               r = put_user(to_book3s(vcpu)->hior, (u64 __user *)reg->addr);
>> +               r = put_user(to_book3s(vcpu)->hior,
>> +                            (u64 __user *)(long)reg->addr);
> 
> Yes and no. It brings me a step further, but not to a working kernel.
> 
>  CHK     include/linux/version.h
>  CHK     include/generated/utsrelease.h
>  CALL    scripts/checksyscalls.sh
>  CC [M]  arch/powerpc/kvm/book3s_pr.o
>  LD [M]  arch/powerpc/kvm/kvm.o
>  Building modules, stage 2.
>  MODPOST 227 modules
> ERROR: "__get_user_bad" [arch/powerpc/kvm/kvm.ko] undefined!

Ah, because you can't get_user u64s I suppose. Sigh. As a quick hack, just comment out the get/put_user lines - you don't care about configuring HIOR on ppc32 anyways. I'll try to come up with something :)


Alex

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