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

From: Jan Kiszka
Subject: [Qemu-devel] Re: [PATCH 4/4] KVM: Rework of guest debug state writing
Date: Thu, 04 Feb 2010 20:21:08 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv: Gecko/20080226 SUSE/ Thunderbird/ Mnenhy/

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.


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

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