Re: [Qemu-devel] [PATCH 4/7 v2] KVM regsync: Add register bitmap parameter to do_kvm_cpu_synchronize_state

[Peter Maydell]

On 24 January 2013 18:17, Scott Wood <address@hidden> wrote:
> On 01/24/2013 06:41:05 AM, Alexander Graf wrote:
>> But maybe the better solution would be a special "write to clear" ONE_REG
>> register to clear specific bits and a big hammer "set" ONE_REG (which we
>> have already) for reset only.
>>
>> That would make things easier, right? Scott, any ideas on this?

> Yes, we should have a ONE_REG write-to-clear TSR.  Maybe a write-to-set
> version as well, in case userspace wants to inject something.  Likewise for
> MCSR.

This would go against the principle we adopted for ARM ONE_REG,
which is that the "registers" accessed this way never have side
effects, so userspace could do a complete migration via
"get complete list of regs; get each reg in list; transfer
all values to remote end; remote end sets each reg".

Obviously PPC isn't bound to abide by the same ground rules
for the ioctl, but I figured I'd mention the principle so
you can decide if you like it :-)

-- PMM