Sorry for spamming. The correct fix appears to reload the DRs (set
KVM_DEBUGREG_RELOAD) in kvm_arch_vcpu_load .
(for me it works)
Regards,
Nadav
Nadav Amit <nadav.amit@xxxxxxxxx> wrote:
> I think the problem lies here:
>
> /*
> * If the guest has used debug registers, at least dr7
> * will be disabled while returning to the host.
> * If we don't have active breakpoints in the host, we don't
> * care about the messed up debug address registers. But if
> * we have some of them active, restore the old state.
> */
> if (hw_breakpoint_active()) {
> hw_breakpoint_restore();
> }
>
> First we need to reload the DRs after we do hw_breakpoint_restore(), no?
> vcpu->arch.switch_db_regs |= KVM_DEBUGREG_RELOAD;
>
> Second, I am unsure whether hw_breakpoint_active() is the correct condition.
>
> In my defense note that my tests did not his this case since I set affinity
> of the VCPUs to physical cores, and prevented other processes from running.
>
> Regards,
> Nadav
>
> Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
>> On 29/01/2016 23:21, Andrew Vagin wrote:
>>> On Thu, Jan 28, 2016 at 02:42:25PM -0800, Andrey Wagin wrote:
>>>> On Thu, Jan 28, 2016 at 10:33:28PM +0100, Paolo Bonzini wrote:
>>>>> On 28/01/2016 09:31, Andrey Wagin wrote:
>>>>>> I tried to print drX registers after a break-point. Looks like they
>>>>>> are set correctly.
>>>>>
>>>>> Can you try this KVM patch?
>>>>
>>>> Looks like it fixes a case when reproducers are running only in VM.
>>>
>>> Actually Oleg's reproducer detects the bug with this patch when they are
>>> rinning only in VM.
>>
>> That's actually a good thing, because the patch was a long shot and I
>> had no clue _why_ it would have fixed the bug. Oleg's reproducer
>> spanning host and a VM actually gives me an idea of what is going on,
>> I'll try to reproduce this week.
>>
>> Paolo
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