Re: [patch 1/3] KVM: task switch: translate guest segment limit to virt-extension byte granular field

[Marcelo Tosatti <mtosatti@redhat.com>]

On Sun, Jul 20, 2008 at 12:22:07PM +0300, Avi Kivity wrote:
> Marcelo Tosatti wrote:
>> If 'g' is one then limit is 4kb granular.
>>
>> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
>>
>> Index: kvm-vmx-checks/arch/x86/kvm/x86.c
>> ===================================================================
>> --- kvm-vmx-checks.orig/arch/x86/kvm/x86.c
>> +++ kvm-vmx-checks/arch/x86/kvm/x86.c
>> @@ -3195,6 +3195,10 @@ static void seg_desct_to_kvm_desct(struc
>>  	kvm_desct->base |= seg_desc->base2 << 24;
>>  	kvm_desct->limit = seg_desc->limit0;
>>  	kvm_desct->limit |= seg_desc->limit << 16;
>> +	if (seg_desc->g) {
>> +		kvm_desct->limit <<= 12;
>> +		kvm_desct->limit |= 0xfff;
>> +	}
>>  	kvm_desct->selector = selector;
>>  	kvm_desct->type = seg_desc->type;
>>  	kvm_desct->present = seg_desc->p;
>>   
>
> This looks good,
>
>> @@ -3222,8 +3226,12 @@ static void get_segment_descritptor_dtab
>>   		if (kvm_seg.unusable)
>>  			dtable->limit = 0;
>> -		else
>> -			dtable->limit = kvm_seg.limit;
>> +		else {
>> +			if (kvm_seg.g)
>> +				dtable->limit = kvm_seg.limit >> 12;
>> +			else
>> +				dtable->limit = kvm_seg.limit;
>> +		}
>>  		dtable->base = kvm_seg.base;
>>  	
>
> But this doesn't.  As far as I can tell, users of  
> get_segment_descritptor_dtable() expect a normalized limit (always in  
> bytes).

Ouch, yes. Here's it:


KVM: task switch: translate guest segment limit to virt-extension byte granular field

If 'g' is one then limit is 4kb granular.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Index: kvm-vmx-checks/arch/x86/kvm/x86.c
===================================================================
--- kvm-vmx-checks.orig/arch/x86/kvm/x86.c
+++ kvm-vmx-checks/arch/x86/kvm/x86.c
@@ -3195,6 +3195,10 @@ static void seg_desct_to_kvm_desct(struc
 	kvm_desct->base |= seg_desc->base2 << 24;
 	kvm_desct->limit = seg_desc->limit0;
 	kvm_desct->limit |= seg_desc->limit << 16;
+	if (seg_desc->g) {
+		kvm_desct->limit <<= 12;
+		kvm_desct->limit |= 0xfff;
+	}
 	kvm_desct->selector = selector;
 	kvm_desct->type = seg_desc->type;
 	kvm_desct->present = seg_desc->p;