[Qemu-devel] Re: [PATCH 4/4] KVM: Rework of guest debug state writing

[Jan Kiszka]

Jan Kiszka wrote:
> Marcelo Tosatti wrote:
>> With kvm-autotest the failure is not sporadic (and the above commit
>> applied): with KVM_SET_GUEST_DEBUG in arch_put_regs all migration 
>> tests fail, without, all of them succeed. 
>>
>> So env->kvm_guest_debug has been zeroed by cpu_x86_init, which means
>> the writeback via KVM_SET_GUEST_DEBUG does almost nothing. It does
>> get_rflags and set_rflags in the kernel.
> 
> Hmm, it also copies debug regs around... BTW, where do we save/restore
> dr0..7 between kernel and user space?
> 
> But that should not be a problem, both shadow as well as effective regs
> should be properly initialized, specifically for a newly created VCPU.

Could you retry after pushing SET_GUEST_DEBUG at the end of
kvm_arch_put_registers? Maybe it is no good idea to run get/set_rflags
without having the sregs properly initialized.

Jan

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux