Re: [Qemu-devel] [RFC] Next gen kvm api

From: Alexander Graf
Date: Tue Feb 07 2012 - 05:04:51 EST

On 07.02.2012, at 07:58, Michael Ellerman wrote:

> On Mon, 2012-02-06 at 13:46 -0600, Scott Wood wrote:
>> On 02/03/2012 04:52 PM, Anthony Liguori wrote:
>>> On 02/03/2012 12:07 PM, Eric Northup wrote:
>>>> On Thu, Feb 2, 2012 at 8:09 AM, Avi Kivity<avi@xxxxxxxxxx> wrote:
>>>> [...]
>>>>> Moving to syscalls avoids these problems, but introduces new ones:
>>>>> - adding new syscalls is generally frowned upon, and kvm will need
>>>>> several
>>>>> - syscalls into modules are harder and rarer than into core kernel code
>>>>> - will need to add a vcpu pointer to task_struct, and a kvm pointer to
>>>>> mm_struct
>>>> - Lost a good place to put access control (permissions on /dev/kvm)
>>>> for which user-mode processes can use KVM.
>>>> How would the ability to use sys_kvm_* be regulated?
>>> Why should it be regulated?
>>> It's not a finite or privileged resource.
>> You're exposing a large, complex kernel subsystem that does very
>> low-level things with the hardware. It's a potential source of exploits
>> (from bugs in KVM or in hardware). I can see people wanting to be
>> selective with access because of that.
> Exactly.
> In a perfect world I'd agree with Anthony, but in reality I think
> sysadmins are quite happy that they can prevent some users from using
> KVM.
> You could presumably achieve something similar with capabilities or
> whatever, but a node in /dev is much simpler.

Well, you could still keep the /dev/kvm node and then have syscalls operate on the fd.

But again, I don't see the problem with the ioctl interface. It's nice, extensible and works great for us.


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at