Re: x86: Hardware breakpoints are not always triggered

From: Andrey Wagin
Date: Thu Jan 28 2016 - 17:42:39 EST


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.

If I execute the reproducer a few times on the host and then execute it
in VM, it exits very fast.

Thanks,
Andrew

>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index c13a64b7d789..32bae1c70a50 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -1612,6 +1612,7 @@ static void svm_sync_dirty_debug_regs(struct kvm_vcpu *vcpu)
> vcpu->arch.dr7 = svm->vmcb->save.dr7;
>
> vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_WONT_EXIT;
> + vcpu->arch.switch_db_regs |= KVM_DEBUGREG_RELOAD;
> set_dr_intercepts(svm);
> }
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index e2951b6edbbc..505a4663b9f4 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -5659,6 +5659,7 @@ static void vmx_sync_dirty_debug_regs(struct kvm_vcpu *vcpu)
> vcpu->arch.dr7 = vmcs_readl(GUEST_DR7);
>
> vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_WONT_EXIT;
> + vcpu->arch.switch_db_regs |= KVM_DEBUGREG_RELOAD;
>
> cpu_based_vm_exec_control = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL);
> cpu_based_vm_exec_control |= CPU_BASED_MOV_DR_EXITING;
>
> Paolo