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From 0ed92ca843fec14757ea7b59f4c83ed52b91b815 Mon Sep 17 00:00:00 2001
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From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
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Date: Wed, 22 Mar 2017 11:26:40 +0100
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Subject: x86: Work around SMI breakages
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RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
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Message-id: <20170322112640.5933-1-dgilbert@redhat.com>
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Patchwork-id: 74427
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O-Subject: [RHEL-7.4 qemu-kvm-rhev PATCH v2] x86: Work around SMI breakages
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Bugzilla: 1420679
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Acked-by: Igor Mammedov <imammedo@redhat.com>
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From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
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This enables the fix added upstream in fc3a1fd7 on 7.3 machine types
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and earlier.
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The reported symptom was that a 7.2->7.4 migration failed with the
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guest rebooting on the destination; 7.2->7.3 worked as did 7.3->7.4
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7.2,7.3,7.4 all have different levels of support for SMI's:
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7.2 basically doesn't support it, but knows enough to set the
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CPU_INTERRUPT_SMI flag.
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7.3 thought it supported SMIs but fails to deliver SMI interrupts
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(see upstream 68c6efe07a) - but it does clear the
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CPU_INTERRUPT_SMI flag when it tries.
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7.4 apparently supports SMIs
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On 7.2 something tries an SMI, but the interrupt never happens,
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but it does leave the CPU_INTERRUPT_SMI flag set - this ends up
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in the migration stream, but it's ignored by 7.2.
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7.2->7.3 sees the CPU_INTERRUPT_SMI, clears the flag but fails
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to actually enter the SMI code. Everything seems to survive,
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but perhaps this explains some of the bugs we hit until we
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disabled the SMI in Seabios in 7.3
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7.2->7.4 sees the CPU_INTERRUPT_SMI and actually takes the SMI,
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landing in what I think is empty SMRAM space, eventually falling
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off the end, triple faulting and rebooting - which is what we hit
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here.
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The (nasty) fix is to reinstate the 7.3 bug for machine types older
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than 7.4; that should keep us compatible with 7.3 and get
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lucky in the same way as we did with 7.2.
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Note: We still have to be careful in the ROMs we provide with 7.4
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because the ROM contents will get migrated whenever we do
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7.4->7.3/7.2 migrates.
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Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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(cherry picked from commit c094723a6ed544df512c4c3fd22d0eec71262886)
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---
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include/hw/i386/pc.h | 5 +++++
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1 file changed, 5 insertions(+)
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diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
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index c88c46a..b69e53c 100644
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--- a/include/hw/i386/pc.h
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+++ b/include/hw/i386/pc.h
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@@ -1042,6 +1042,11 @@ extern void igd_passthrough_isa_bridge_create(PCIBus *bus, uint16_t gpu_dev_id);
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.driver = TYPE_X86_CPU,\
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.property = "cpuid-0xb",\
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.value = "off",\
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+ },\
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+ { /* PC_RHEL7_3_COMPAT */ \
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+ .driver = TYPE_X86_CPU,\
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+ .property = "kvm-no-smi-migration",\
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+ .value = "on",\
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},
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#define PC_RHEL7_2_COMPAT \
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--
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1.8.3.1
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