From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH] KVM: VMX: Update instruction length on intercepted BP Date: Sun, 14 Feb 2010 11:26:31 +0100 Message-ID: <4B77CFD7.9080504@web.de> References: <4B767160.4070609@web.de> <20100214075303.GF2511@redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig2AFC31C363C29AE285D02511" Cc: Avi Kivity , Marcelo Tosatti , kvm To: Gleb Natapov Return-path: Received: from fmmailgate02.web.de ([217.72.192.227]:46987 "EHLO fmmailgate02.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753410Ab0BNK0d (ORCPT ); Sun, 14 Feb 2010 05:26:33 -0500 In-Reply-To: <20100214075303.GF2511@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig2AFC31C363C29AE285D02511 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Gleb Natapov wrote: > On Sat, Feb 13, 2010 at 10:31:12AM +0100, Jan Kiszka wrote: >> From: Jan Kiszka >> >> We intercept #BP while in guest debugging mode. As VM exists due to >> intercepted exceptions do not necessarily come with valid >> idt_vectoring, we have to update event_exit_inst_len explicitly in suc= h >> cases. At least in the absence of migration, this ensures that >> re-injections of #BP will find and use the correct instruction length.= >> > event_exit_inst_len is only used for event reinjection. Since event > intercepted here will not be reinjected why updating event_exit_inst_le= n > is needed here? In guest debugging mode a #BP exception is always reported to user space to find out what caused it. If it was the guest itself, the exception is reinjected, on older kernels via KVM_SET_GUEST_DEBUG and since 2.6.33 via KVM_SET_VCPU_EVENTS (the latter requires some qemu patch that I will post later). As we currently do not update event_exit_inst_len on #BP exits, reinjecting fails unless event_exit_inst_len happens to be 1 from some other exit. Jan >=20 >> Signed-off-by: Jan Kiszka >> --- >> >> Please consider for stable, this fixes guest debugging scenarios. >> >> arch/x86/kvm/vmx.c | 4 ++++ >> 1 files changed, 4 insertions(+), 0 deletions(-) >> >> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >> index f82b072..e9f64e8 100644 >> --- a/arch/x86/kvm/vmx.c >> +++ b/arch/x86/kvm/vmx.c >> @@ -2775,6 +2775,8 @@ static int handle_rmode_exception(struct kvm_vcp= u *vcpu, >> kvm_queue_exception(vcpu, vec); >> return 1; >> case BP_VECTOR: >> + to_vmx(vcpu)->vcpu.arch.event_exit_inst_len =3D >> + vmcs_read32(VM_EXIT_INSTRUCTION_LEN); >> if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) >> return 0; >> /* fall through */ >> @@ -2897,6 +2899,8 @@ static int handle_exception(struct kvm_vcpu *vcp= u) >> kvm_run->debug.arch.dr7 =3D vmcs_readl(GUEST_DR7); >> /* fall through */ >> case BP_VECTOR: >> + vmx->vcpu.arch.event_exit_inst_len =3D >> + vmcs_read32(VM_EXIT_INSTRUCTION_LEN); >> kvm_run->exit_reason =3D KVM_EXIT_DEBUG; >> kvm_run->debug.arch.pc =3D vmcs_readl(GUEST_CS_BASE) + rip; >> kvm_run->debug.arch.exception =3D ex_no; >> >=20 >=20 >=20 > -- > Gleb. --------------enig2AFC31C363C29AE285D02511 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org iEYEARECAAYFAkt3z9cACgkQitSsb3rl5xRapQCgv0Ca0jPCJsdlpKRzf0bqU4fN Z3oAn3G9LWrtO1v24uGueb9YEVC2Ls07 =KEFx -----END PGP SIGNATURE----- --------------enig2AFC31C363C29AE285D02511--