From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=41109 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PkMoC-0000nI-0E for qemu-devel@nongnu.org; Tue, 01 Feb 2011 15:26:41 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PkMoA-000221-QZ for qemu-devel@nongnu.org; Tue, 01 Feb 2011 15:26:39 -0500 Received: from fmmailgate02.web.de ([217.72.192.227]:33498) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PkMoA-00021D-DC for qemu-devel@nongnu.org; Tue, 01 Feb 2011 15:26:38 -0500 Message-ID: <4D486C5D.4010806@web.de> Date: Tue, 01 Feb 2011 21:26:05 +0100 From: Jan Kiszka MIME-Version: 1.0 References: <1296587851-19621-1-git-send-email-glommer@redhat.com> In-Reply-To: <1296587851-19621-1-git-send-email-glommer@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigE9A71C5F75BDAD91D2BAA21D" Sender: jan.kiszka@web.de Subject: [Qemu-devel] Re: [PATCH] make tsc stable over migration and machine start List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Glauber Costa Cc: mtosatti@redhat.com, qemu-devel@nongnu.org, kvm@vger.kernel.org, avi@redhat.com This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigE9A71C5F75BDAD91D2BAA21D Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: quoted-printable On 2011-02-01 20:17, Glauber Costa wrote: > If the machine is stopped, we should not record two different tsc value= s > upon a save operation. The same problem happens with kvmclock. >=20 > But kvmclock is taking a different diretion, being now seen as a separa= te > device. Since this is unlikely to happen with the tsc, I am taking the > approach here of simply registering a handler for state change, and > using a per-CPUState variable that prevents double updates for the TSC.= >=20 > Signed-off-by: Glauber Costa > --- > target-i386/cpu.h | 1 + > target-i386/kvm.c | 19 ++++++++++++++++++- > 2 files changed, 19 insertions(+), 1 deletions(-) >=20 > diff --git a/target-i386/cpu.h b/target-i386/cpu.h > index 6d619e8..7f1c4f8 100644 > --- a/target-i386/cpu.h > +++ b/target-i386/cpu.h > @@ -732,6 +732,7 @@ typedef struct CPUX86State { > uint32_t sipi_vector; > uint32_t cpuid_kvm_features; > uint32_t cpuid_svm_features; > + uint8_t update_tsc; bool please. > =20 > /* in order to simplify APIC support, we leave this pointer to the= > user */ > diff --git a/target-i386/kvm.c b/target-i386/kvm.c > index ecb8405..c3925be 100644 > --- a/target-i386/kvm.c > +++ b/target-i386/kvm.c > @@ -302,6 +302,16 @@ void kvm_inject_x86_mce(CPUState *cenv, int bank, = uint64_t status, > =20 > static int _kvm_arch_init_vcpu(CPUState *env); > =20 > +static void cpu_update_state(void *opaque, int running, int reason) > +{ > + CPUState *env =3D opaque; > + > + if (!running) { > + env->update_tsc =3D 1; > + } > +} > + > + Additional blank line. > int kvm_arch_init_vcpu(CPUState *env) > { > int r; > @@ -444,6 +454,8 @@ int kvm_arch_init_vcpu(CPUState *env) > } > #endif > =20 > + qemu_add_vm_change_state_handler(cpu_update_state, env); > + > return kvm_vcpu_ioctl(env, KVM_SET_CPUID2, &cpuid_data); > } > =20 > @@ -1093,7 +1105,12 @@ static int kvm_get_msrs(CPUState *env) > msrs[n++].index =3D MSR_STAR; > if (kvm_has_msr_hsave_pa(env)) > msrs[n++].index =3D MSR_VM_HSAVE_PA; > - msrs[n++].index =3D MSR_IA32_TSC; > + > + if (env->update_tsc) { > + msrs[n++].index =3D MSR_IA32_TSC; > + env->update_tsc =3D 0; > + } > + > #ifdef TARGET_X86_64 > if (lm_capable_kernel) { > msrs[n++].index =3D MSR_CSTAR; Not quite the logic I'm using for kvmclock: cpu_update_state() if running tsc_valid =3D false; kvm_get_msrs() ... if (!tsc_valid) read_tsc tsc_valid =3D !vm_running; That ensure we always read the tsc while the VM is running, and not only after it was stopped (might otherwise be "surprising" when once visualizing the MSRs). Jan --------------enigE9A71C5F75BDAD91D2BAA21D Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.15 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org/ iEYEARECAAYFAk1IbF8ACgkQitSsb3rl5xRGZgCfTFbCx4VTHOdS8SZsAkRCA0NI /UYAoIME5LMMRViHKbsegn4Q0ecNmNN6 =lmMH -----END PGP SIGNATURE----- --------------enigE9A71C5F75BDAD91D2BAA21D--