Bug#707257: linux-image-3.8-1-686-pae: KVM crashes with "entry failed, hardware error 0x80000021"

[Stefan Pietsch <stefan.pietsch@lsexperts.de>]

On 26.06.2013 12:47, Gleb Natapov wrote:
> On Mon, Jun 24, 2013 at 10:42:57PM +0200, Stefan Pietsch wrote:
>> On 24.06.2013 14:30, Gleb Natapov wrote:
>>> On Mon, Jun 24, 2013 at 01:59:34PM +0200, Stefan Pietsch wrote:
>>>> As soon as I remove "kvmvapic.bin" the virtual machine boots with
>>>> qemu-kvm 1.5.0. I just verified this with Linux kernel 3.10.0-rc5.
>>>> "emulate_invalid_guest_state=0" or "emulate_invalid_guest_state=1" make
>>>> no difference.
>>>>
>>>> Please send your patches.
>>> Here it is, run with it and kvmvapic.bin present. See what is printed in
>>> dmesg after the failure.
>>>
>>>
>>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>>> index f4a5b3f..65488a4 100644
>>> --- a/arch/x86/kvm/vmx.c
>>> +++ b/arch/x86/kvm/vmx.c
>>> @@ -3385,6 +3385,7 @@ static void vmx_get_segment(struct kvm_vcpu *vcpu,
>>>  {
>>>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
>>>  	u32 ar;
>>> +	unsigned long rip;
>>>  
>>>  	if (vmx->rmode.vm86_active && seg != VCPU_SREG_LDTR) {
>>>  		*var = vmx->rmode.segs[seg];
>>> @@ -3408,6 +3409,9 @@ static void vmx_get_segment(struct kvm_vcpu *vcpu,
>>>  	var->db = (ar >> 14) & 1;
>>>  	var->g = (ar >> 15) & 1;
>>>  	var->unusable = (ar >> 16) & 1;
>>> +	rip = kvm_rip_read(vcpu);
>>> +	if ((rip == 0xc101611c || rip == 0xc101611a) && seg == VCPU_SREG_FS)
>>> +		printk("base=%p limit=%p selector=%x ar=%x\n", var->base, var->limit, var->selector, ar);
>>>  }
>>>  
>>>  static u64 vmx_get_segment_base(struct kvm_vcpu *vcpu, int seg)
>>
>>
>> Booting kernel Linux 3.10-rc5 with your patch applied produces these
>> messages in dmesg when starting a virtual machine:
>>
>> emulate_invalid_guest_state=0
>> [  118.732151] base=ffff0000 limit=  (null) selector=f0000fff ar=0
>> [  118.732341] base=ffff0000 limit=  (null) selector=f0000fff ar=0
>>
> I've butchered printk format, but it gives me the idea of what is going
> on anyway. Can you try the patch below with
> emulate_invalid_guest_state=0|1?
> 
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index f4a5b3f..eb062ce 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -3395,19 +3395,20 @@ static void vmx_get_segment(struct kvm_vcpu *vcpu,
>  		var->selector = vmx_read_guest_seg_selector(vmx, seg);
>  		return;
>  	}
> +
>  	var->base = vmx_read_guest_seg_base(vmx, seg);
>  	var->limit = vmx_read_guest_seg_limit(vmx, seg);
>  	var->selector = vmx_read_guest_seg_selector(vmx, seg);
>  	ar = vmx_read_guest_seg_ar(vmx, seg);
> +	var->unusable = (ar >> 16) & 1;
>  	var->type = ar & 15;
>  	var->s = (ar >> 4) & 1;
>  	var->dpl = (ar >> 5) & 3;
> -	var->present = (ar >> 7) & 1;
> +	var->present = !var->unusable;
>  	var->avl = (ar >> 12) & 1;
>  	var->l = (ar >> 13) & 1;
>  	var->db = (ar >> 14) & 1;
>  	var->g = (ar >> 15) & 1;
> -	var->unusable = (ar >> 16) & 1;
>  }
>  
>  static u64 vmx_get_segment_base(struct kvm_vcpu *vcpu, int seg)


Kernel 3.10-rc5 with your latest patch applied can successfully boot the
virtual machine with emulate_invalid_guest_state 0 or 1.