From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55396) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V1DhJ-0002ER-I8 for qemu-devel@nongnu.org; Mon, 22 Jul 2013 06:50:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1V1DhI-0003Pm-IN for qemu-devel@nongnu.org; Mon, 22 Jul 2013 06:50:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:32954) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V1DhI-0003PY-Ag for qemu-devel@nongnu.org; Mon, 22 Jul 2013 06:50:32 -0400 From: Juan Quintela In-Reply-To: <1374475799-18523-1-git-send-email-owasserm@redhat.com> (Orit Wasserman's message of "Mon, 22 Jul 2013 09:49:58 +0300") References: <1374475799-18523-1-git-send-email-owasserm@redhat.com> Date: Mon, 22 Jul 2013 12:50:29 +0200 Message-ID: <87wqoij2bu.fsf@elfo.elfo> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH 1/2] Fix real mode guest migration Reply-To: quintela@redhat.com List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Orit Wasserman Cc: aliguori@us.ibm.com, ehabkost@redhat.com, gleb@redhat.com, mtosatti@redhat.com, qemu-devel@nongnu.org, pbonzini@redhat.com, afaerber@suse.de Orit Wasserman wrote: > Older KVM versions save CS dpl value to an invalid value for real mode guests > (0x3). This patch detect this situation when loading CPU state and set all the > segments dpl to zero. > This will allow migration from older KVM on host without unrestricted guest > to hosts with restricted guest support. > For example migration from a Penryn host (with kernel 2.6.32) to > a Westmere host. > > Signed-off-by: Orit Wasserman > --- > target-i386/machine.c | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > diff --git a/target-i386/machine.c b/target-i386/machine.c > index 3659db9..7e95829 100644 > --- a/target-i386/machine.c > +++ b/target-i386/machine.c > @@ -260,6 +260,24 @@ static int cpu_post_load(void *opaque, int version_id) > CPUX86State *env = &cpu->env; > int i; > > + /* > + Real mode guest segments register DPL should be zero. > + Older KVM version were setting it worngly. s/worngly/wrongly/ on both patches > + Fixing it will allow live migration from such host that don't have > + restricted guest support to an host with unrestricted guest support > + (otherwise the migration will fail with invalid guest state > + error). > + */ > + if (!(env->cr[0] & CR0_PE_MASK) && > + (env->segs[R_CS].flags >> DESC_DPL_SHIFT & 3) != 0) { > + env->segs[R_CS].flags &= ~(env->segs[R_CS].flags & DESC_DPL_MASK); > + env->segs[R_DS].flags &= ~(env->segs[R_DS].flags & DESC_DPL_MASK); > + env->segs[R_ES].flags &= ~(env->segs[R_ES].flags & DESC_DPL_MASK); > + env->segs[R_FS].flags &= ~(env->segs[R_FS].flags & DESC_DPL_MASK); > + env->segs[R_GS].flags &= ~(env->segs[R_GS].flags & DESC_DPL_MASK); > + env->segs[R_SS].flags &= ~(env->segs[R_SS].flags & DESC_DPL_MASK); > + } > + > /* XXX: restore FPU round state */ > env->fpstt = (env->fpus_vmstate >> 11) & 7; > env->fpus = env->fpus_vmstate & ~0x3800;