From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44157) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fTcub-0006cl-10 for qemu-devel@nongnu.org; Thu, 14 Jun 2018 20:48:22 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fTcuX-0006BU-Rl for qemu-devel@nongnu.org; Thu, 14 Jun 2018 20:48:21 -0400 Date: Fri, 15 Jun 2018 10:14:31 +1000 From: David Gibson Message-ID: <20180615001431.GF4129@umbus.fritz.box> References: <152901299450.252222.14219708016930421485.stgit@bahia.lan> <152901304242.252222.9947658955703347553.stgit@bahia.lan> <20180615000225.GC4129@umbus.fritz.box> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="924gEkU1VlJlwnwX" Content-Disposition: inline In-Reply-To: <20180615000225.GC4129@umbus.fritz.box> Subject: Re: [Qemu-devel] [PATCH 3/5] spapr_cpu_core: add missing rollback on realization path List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Greg Kurz Cc: qemu-devel@nongnu.org, qemu-ppc@nongnu.org, =?iso-8859-1?Q?C=E9dric?= Le Goater --924gEkU1VlJlwnwX Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Jun 15, 2018 at 10:02:25AM +1000, David Gibson wrote: > On Thu, Jun 14, 2018 at 11:50:42PM +0200, Greg Kurz wrote: > > The spapr_realize_vcpu() function doesn't rollback in case of error. > > This isn't a problem with coldplugged CPUs because the machine won't > > start and QEMU will exit. Hotplug is a different story though: the > > CPU thread is started under object_property_set_bool() and it assumes > > it can access the CPU object. > >=20 > > If icp_create() fails, we return an error without unregistering the > > reset handler for this CPU, and we let the underlying QEMU thread for > > this CPU alive. Since spapr_cpu_core_realize() doesn't care to unrealize > > already realized CPUs either, but happily frees all of them anyway, the > > CPU thread crashes instantly: > >=20 > > (qemu) device_add host-spapr-cpu-core,core-id=3D1,id=3Dgku > > GKU: failing icp_create (cpu 0x11497fd0) > > ^^^^^^^^^^ > > Program received signal SIGSEGV, Segmentation fault. > > [Switching to Thread 0x7fffee3feaa0 (LWP 24725)] > > 0x00000000104c8374 in object_dynamic_cast_assert (obj=3D0x11497fd0, > > ^^^^^^^^^^^^^^ > > pointer to the CPU object > > 623 trace_object_dynamic_cast_assert(obj ? obj->class->type->na= me > > (gdb) p obj->class->type > > $1 =3D (Type) 0x0 > > (gdb) p * obj > > $2 =3D {class =3D 0x10ea9c10, free =3D 0x11244620, > > ^^^^^^^^^^ > > should be g_free > > (gdb) p g_free > > $3 =3D {} 0x7ffff282bef0 > >=20 > > obj is a dangling pointer to the CPU that was just destroyed in > > spapr_cpu_core_realize(). > >=20 > > This patch adds proper rollback to both spapr_realize_vcpu() and > > spapr_cpu_core_realize(). > >=20 > > Signed-off-by: Greg Kurz >=20 > Applied to ppc-for-3.0, since it definitely looks to fix some > problems. Uh.. actually it has a definite bug - the first exit point will call g_free() on an uninitialized spapr_cpu. I fixed it up with a NULL initialization in my tree. >=20 > > --- > > hw/ppc/spapr_cpu_core.c | 12 ++++++++++-- > > 1 file changed, 10 insertions(+), 2 deletions(-) > >=20 > > diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c > > index 003c4c5a79d2..04c818a6ecac 100644 > > --- a/hw/ppc/spapr_cpu_core.c > > +++ b/hw/ppc/spapr_cpu_core.c > > @@ -159,12 +159,16 @@ static void spapr_realize_vcpu(PowerPCCPU *cpu, s= PAPRMachineState *spapr, > > spapr_cpu->icp =3D icp_create(OBJECT(cpu), spapr->icp_type, > > XICS_FABRIC(spapr), &local_err); > > if (local_err) { > > - goto error; > > + goto error_unregister; > > } > > =20 > > return; > > =20 > > +error_unregister: > > + qemu_unregister_reset(spapr_cpu_reset, cpu); > > + cpu_remove_sync(CPU(cpu)); >=20 > I'm a little unclear on exactly what init the cpu_remove_sync() is > mirroring, though. >=20 > > error: > > + g_free(spapr_cpu); > > error_propagate(errp, local_err); > > } > > =20 > > @@ -222,11 +226,15 @@ static void spapr_cpu_core_realize(DeviceState *d= ev, Error **errp) > > for (j =3D 0; j < cc->nr_threads; j++) { > > spapr_realize_vcpu(sc->threads[j], spapr, &local_err); > > if (local_err) { > > - goto err; > > + goto err_unrealize; > > } > > } > > return; > > =20 > > +err_unrealize: > > + while (--j >=3D 0) { > > + spapr_unrealize_vcpu(sc->threads[i]); > > + } > > err: > > while (--i >=3D 0) { > > obj =3D OBJECT(sc->threads[i]); > >=20 >=20 --=20 David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson --924gEkU1VlJlwnwX Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEdfRlhq5hpmzETofcbDjKyiDZs5IFAlsjBOcACgkQbDjKyiDZ s5KsXw/+IsGexI6d1Ka+ZjO9EpuIx3iUirTKD9rnra1SrjZN/HvtkdXmD+LbcLwW KVnXHcmABW31MRQBwDeT3G84+rjZqPl7aMS9IJpBGduFGdyB2X0KumITDWFjDaql A7qHwlxEQrE7qO7zME1Bhz97O2ovikFwkEn7R+dIGgGCKuI8d6M7fH8F5vhC/1ys 3XSz61QanqZbM1x5+1VdhwIa/hduRZ8n7OgMkPZEEfjVWMLTT80jScZ9OjBohyEP 03tfiYyLuGdE5ovhV6hEuL8GDV9yMazRvj8fEULj7cr6l/xPbFz0V27lfBSIPtiy ikshHHMTZ9t8NHUcDHA16OtD+EBETJ5QsU8lopgHKLOGEY9rU9dM7FbUyvE8taUa 5cDqg1xZCjKhZ4QF3VST4sE03l6ozzoVtsCpjlgDd+ZG2oAlsBR62Co8pzmBe0DD KL8iuBQUH+xjvNtQtXXfdBTmXbhCB5uRQf8JaEp6Ir7Hx9fEHKPOb9Az1MgMyeO8 ml6H11Ck3Hs50Om8S6J/ol6UAAKDaQkzd/fpu2ce1u00irYhxG7IO2tAdHGtaZ1P +ydx0mCgrWb+vn3f33lUgp/wFpNBj4WMMX+QeXPvG2hgE3RyajDEdkQF/Hl+thcf nTyeMT9hC2m7fReNqDxbPGGElgOyHV/XRZH4T2Jo9MUULmHM8i0= =Gjyk -----END PGP SIGNATURE----- --924gEkU1VlJlwnwX--