[RFC PATCH] KVM: arm/arm64: Don't let userspace update CNTVOFF once guest is running

On 29 June 2015 at 18:20, Claudio Fontana [off-list ref] wrote:

On 26.06.2015 06:49, Jan Kiszka wrote:

quoted

QEMU has the concept of write-back levels: KVM_PUT_RUNTIME_STATE,
KVM_PUT_RESET_STATE and KVM_PUT_FULL_STATE. I suspect this registers is
just sorted into the wrong category, thus written as part of the
RUNTIME_STATE. We had such bug patterns during the x86 maturing phase as
well.

It seems that QEMU target-arm ignores the level parameter to
kvm_arch_put_registers completely.

Is it intended?

Yes, sort of. We don't in general know anything about the semantics
of most of the system registers. It should always be safe to
read them all out of the kernel and write them back...

-- PMM