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From c576ee9550d38273808c2055803f3a254655753e Mon Sep 17 00:00:00 2001
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From: Orit Wasserman <owasserm@redhat.com>
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Date: Wed, 9 Oct 2013 10:09:10 +0200
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Subject: [PATCH 15/25] Fix real mode guest migration
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RH-Author: Orit Wasserman <owasserm@redhat.com>
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Message-id: <1381313355-15641-6-git-send-email-owasserm@redhat.com>
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Patchwork-id: 54801
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O-Subject: [RHEL7.0 qemu-kvm v2 05/10] Fix real mode guest migration
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Bugzilla: 921465
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Juan Quintela <quintela@redhat.com>
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Older KVM versions save CS dpl value to an invalid value for real mode guests
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(0x3). This patch detect this situation when loading CPU state and set all the
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segments dpl to zero.
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This will allow migration from older KVM on host without unrestricted guest
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to hosts with restricted guest support.
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For example migration from a Penryn host (with kernel 2.6.32) to
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a Westmere host (for real mode guest) will fail with "kvm: unhandled exit 80000021".
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Signed-off-by: Orit Wasserman <owasserm@redhat.com>
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Reviewed-by: Juan Quintela <quintela@redhat.com>
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Signed-off-by: Juan Quintela <quintela@redhat.com>
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(cherry picked from commit 444ba6797ef6ef331fe9fd34309b1ec59caaede3)
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---
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target-i386/machine.c | 18 ++++++++++++++++++
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1 file changed, 18 insertions(+)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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target-i386/machine.c | 18 ++++++++++++++++++
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1 files changed, 18 insertions(+), 0 deletions(-)
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diff --git a/target-i386/machine.c b/target-i386/machine.c
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index ecf1617..079a132 100644
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--- a/target-i386/machine.c
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+++ b/target-i386/machine.c
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@@ -260,6 +260,24 @@ static int cpu_post_load(void *opaque, int version_id)
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CPUX86State *env = &cpu->env;
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int i;
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+ /*
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+ * Real mode guest segments register DPL should be zero.
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+ * Older KVM version were setting it wrongly.
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+ * Fixing it will allow live migration from such host that don't have
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+ * restricted guest support to a host with unrestricted guest support
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+ * (otherwise the migration will fail with invalid guest state
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+ * error).
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+ */
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+ if (!(env->cr[0] & CR0_PE_MASK) &&
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+ (env->segs[R_CS].flags >> DESC_DPL_SHIFT & 3) != 0) {
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+ env->segs[R_CS].flags &= ~(env->segs[R_CS].flags & DESC_DPL_MASK);
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+ env->segs[R_DS].flags &= ~(env->segs[R_DS].flags & DESC_DPL_MASK);
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+ env->segs[R_ES].flags &= ~(env->segs[R_ES].flags & DESC_DPL_MASK);
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+ env->segs[R_FS].flags &= ~(env->segs[R_FS].flags & DESC_DPL_MASK);
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+ env->segs[R_GS].flags &= ~(env->segs[R_GS].flags & DESC_DPL_MASK);
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+ env->segs[R_SS].flags &= ~(env->segs[R_SS].flags & DESC_DPL_MASK);
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+ }
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+
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/* XXX: restore FPU round state */
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env->fpstt = (env->fpus_vmstate >> 11) & 7;
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env->fpus = env->fpus_vmstate & ~0x3800;
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--
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1.7.1
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