From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [PATCH 2/2] KVM: SVM: Make stepping out of NMI handlers more
 robust
Date: Wed, 17 Feb 2010 15:49:16 +0200
Message-ID: <20100217134916.GA14767@redhat.com>
References: <cover.1266257833.git.jan.kiszka@siemens.com>
 <8cb458e40c9d594f27975b10bb24ecb9a90d8102.1266257833.git.jan.kiszka@siemens.com>
 <20100216080436.GX2995@redhat.com>
 <4B7A6210.5060606@siemens.com>
 <20100216093416.GA2995@redhat.com>
 <4B7A692B.8050207@siemens.com>
 <20100216094954.GB2995@redhat.com>
 <4B7A6E03.2020606@siemens.com>
 <20100216100858.GF2995@redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Avi Kivity <avi@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>,
	kvm <kvm@vger.kernel.org>
To: Jan Kiszka <jan.kiszka@siemens.com>
Return-path: <kvm-owner@vger.kernel.org>
Received: from mx1.redhat.com ([209.132.183.28]:58641 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S934294Ab0BQNt0 (ORCPT <rfc822;kvm@vger.kernel.org>);
	Wed, 17 Feb 2010 08:49:26 -0500
Content-Disposition: inline
In-Reply-To: <20100216100858.GF2995@redhat.com>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

On Tue, Feb 16, 2010 at 12:08:58PM +0200, Gleb Natapov wrote:
> > > 
> > >> Besides this, proper #DB forwarding to the guest was missing.
> > > During NMI injection? How to reproduce?
> > 
> > Inject, e.g., an NMI over code with TF set. A bit harder is placing a
> > guest HW breakpoint at the spot the NMI handler returns to.
> > 
> Will try to reproduce.
> 
How can I make gdb to run debugged process with TF set? Is this patch
fixes it:


diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 52f78dd..b85b200 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -109,6 +109,7 @@ struct vcpu_svm {
 	struct nested_state nested;
 
 	bool nmi_singlestep;
+	bool nmi_singlestep_tf;
 };
 
 /* enable NPT for AMD64 and X86 with PAE */
@@ -1221,9 +1222,14 @@ static int db_interception(struct vcpu_svm *svm)
 
 	if (svm->nmi_singlestep) {
 		svm->nmi_singlestep = false;
-		if (!(svm->vcpu.guest_debug & KVM_GUESTDBG_SINGLESTEP))
+		if (!(svm->vcpu.guest_debug & KVM_GUESTDBG_SINGLESTEP)) {
 			svm->vmcb->save.rflags &=
 				~(X86_EFLAGS_TF | X86_EFLAGS_RF);
+			if (svm->nmi_singlestep_tf) {
+				svm->vmcb->save.rflags |= X86_EFLAGS_TF;
+				kvm_queue_exception(&svm->vcpu, DB_VECTOR);
+			}
+		}
 		update_db_intercept(&svm->vcpu);
 	}
 
@@ -2586,6 +2592,7 @@ static void enable_nmi_window(struct kvm_vcpu *vcpu)
 	   possible problem (IRET or exception injection or interrupt
 	   shadow) */
 	svm->nmi_singlestep = true;
+	svm->nmi_singlestep_tf = (svm->vmcb->save.rflags | X86_EFLAGS_TF);
 	svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF);
 	update_db_intercept(vcpu);
 }
--
			Gleb.