Radim,
On Fri, Feb 2, 2018 at 1:04 PM, Radim Krčmář <rkrcmar@xxxxxxxxxx> wrote:
> Right, it's unlikely that we'll be doing more checks on kvm_valid_regs,
> so I've moved it here and replaced the block with
>
> if (vcpu->run->kvm_valid_regs & ~KVM_SYNC_X86_VALID_FIELDS) {
> r = -EINVAL;
> goto out;
> }
>
> You can see the result in kvm/queue.
Thanks for cleaning that up & queuing the commits!
> Btw. the userspace doesn't know what the next userspace exit is going to
> be, so it the purpose of kvm_valid_regs to avoid needless writes of
> registers on old userspaces?
If you mean userspace agents that don't have code to use SYNC_REGS,
then yes. Or new userspace agents that have not enabled features that
use S_R or features that only need a subset of available register
sets. Originally I had FPU and debug_regs as well and expected that
those would not be as broadly used and wanted to enable turning them
on/off. Also, I wanted to keep the flexibility because I have related
patches extending and building on SYNC_REGS that I will be sending for
review in the near future.
thanks again,
Ken
