On 09.03.2010, at 14:00, Avi Kivity wrote:
> On 03/08/2010 08:03 PM, Alexander Graf wrote:
>> MOL uses its own hypercall interface to call back into userspace when
>> the guest wants to do something.
>>
>> So let's implement that as an exit reason, specify it with a CAP and
>> only really use it when userspace wants us to.
>>
>> The only user of it so far is MOL.
>>
>> Signed-off-by: Alexander Graf<agraf@xxxxxxx>
>>
>> ---
>>
>> v1 -> v2:
>>
>> - Add documentation for OSI exit struct
>> ---
>> Documentation/kvm/api.txt | 13 +++++++++++++
>> arch/powerpc/include/asm/kvm_book3s.h | 5 +++++
>> arch/powerpc/include/asm/kvm_host.h | 2 ++
>> arch/powerpc/kvm/book3s.c | 24 ++++++++++++++++++------
>> arch/powerpc/kvm/powerpc.c | 12 ++++++++++++
>> include/linux/kvm.h | 6 ++++++
>> 6 files changed, 56 insertions(+), 6 deletions(-)
>>
>> diff --git a/Documentation/kvm/api.txt b/Documentation/kvm/api.txt
>> index 6a19ab6..b2129e8 100644
>> --- a/Documentation/kvm/api.txt
>> +++ b/Documentation/kvm/api.txt
>> @@ -932,6 +932,19 @@ s390 specific.
>>
>> powerpc specific.
>>
>> + /* KVM_EXIT_OSI */
>> + struct {
>> + __u64 gprs[32];
>> + } osi;
>> +
>> +MOL uses a special hypercall interface it calls 'OSI'. To enable it, we catch
>> +hypercalls and exit with this exit struct that contains all the guest gprs.
>> +
>> +If exit_reason is KVM_EXIT_OSI, then the vcpu has triggered such a hypercall.
>> +Userspace can now handle the hypercall and when it's done modify the gprs as
>> +necessary. Upon guest entry all guest GPRs will then be replaced by the values
>> +in this struct.
>> +
>>
>
> That's migration unsafe. There may not be next guest entry on this host.
It's as unsafe as MMIO then.
> Is using KVM_[GS]ET_REGS problematic for some reason?
It's two additional ioctls for no good reason. We know the interface, so we can model towards it.
Alex--
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