linux-kernel - Re: x86: Hardware breakpoints are not always triggered

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Message-ID: <20160128224224.GA10028@gmail.com>
Date:	Thu, 28 Jan 2016 14:42:25 -0800
From:	Andrey Wagin <avagin@...il.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Oleg Nesterov <oleg@...hat.com>,
	"criu@...nvz.org" <criu@...nvz.org>, kvm@...r.kernel.org
Subject: Re: x86: Hardware breakpoints are not always triggered

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