Re: [PATCH] libkvm-s390

[Avi Kivity <avi@qumranet.com>]

Christian Borntraeger wrote:
>   
>>> +#define LIBKVM_S390_ORIGIN (0UL)
>>>       
>> Thought you got rid of that?
>>     
>
> Sort of. We have the kernel code ready to move away the guest from address 0. 
> To achieve that goal we use the offset and limit field in the control block.
> Thing is, on older models the offset and limit must be < 128GB. that means we 
> still cannot use randomly allocated memory. LIBKVM_S390_ORIGIN=1M,2M or 16M 
> would be perfectly fine, 2TB (typical malloc space) is not.
> Furthermore, this change is still in kvm.git, but not in Linus git. 
> Therefore, we would like to keep the guest at 0 and fix that at a later time, 
> ok?
>   

Certainly.  I suggest exposing this via a KVM_CAP_blah and adapting at 
runtime.

Placing the guest at offset zero is dangerous, since all a guest has to 
do is place a function at guest physical address zero and wait for a 
kernel bug that calls a null function pointer (at least, it would behave 
like that on x86, provided no-execute was disabled; it may well be that 
s390 has additional protection).

-- 
error compiling committee.c: too many arguments to function