From 3e0f343e05796e009c0cf2b31cf12c59282bcd63 Mon Sep 17 00:00:00 2001

From: Igor Mammedov <imammedo@redhat.com>

Date: Wed, 24 May 2017 07:57:44 +0200

Subject: [PATCH 2/6] pc/fwcfg: unbreak migration from qemu-2.5 and qemu-2.6

 during firmware boot

RH-Author: Igor Mammedov <imammedo@redhat.com>

Message-id: <1495612665-46614-2-git-send-email-imammedo@redhat.com>

Patchwork-id: 75405

O-Subject: [RHEL7.4 qemu-kvm-rhev v2 1/2] pc/fwcfg: unbreak migration from qemu-2.5 and qemu-2.6 during firmware boot

Bugzilla: 1441394

RH-Acked-by: Laszlo Ersek <lersek@redhat.com>

RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>

RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

Since 2.7 commit (b2a575a Add optionrom compatible with fw_cfg DMA version)

regressed migration during firmware exection time by

abusing fwcfg.dma_enabled property to decide loading

dma version of option rom AND by mistake disabling DMA

for 2.6 and earlier globally instead of only for option rom.

so 2.6 machine type guest is broken when it already runs

firmware in DMA mode but migrated to qemu-2.7(pc-2.6)

at that time;

a) qemu-2.6:pc2.6 (fwcfg.dma=on,firmware=dma,oprom=ioport)

b) qemu-2.7:pc2.6 (fwcfg.dma=off,firmware=ioport,oprom=ioport)

  to:   a     b

from

a       OK   FAIL

b       OK   OK

So we currently have broken forward migration from

qemu-2.6 to qemu-2.[789] that however could be fixed

for 2.10 by re-enabling DMA for 2.[56] machine types

and allowing dma capable option rom only since 2.7.

As result qemu should end up with:

c) qemu-2.10:pc2.6 (fwcfg.dma=on,firmware=dma,oprom=ioport)

   to:  a     b    c

from

a      OK   FAIL  OK

b      OK   OK    OK

c      OK   FAIL  OK

where forward migration from qemu-2.6 to qemu-2.10 should

work again leaving only qemu-2.[789]:pc-2.6 broken.

Reported-by: Eduardo Habkost <ehabkost@redhat.com>

Analyzed-by: Laszlo Ersek <lersek@redhat.com>

Signed-off-by: Igor Mammedov <imammedo@redhat.com>

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

(cherry picked from commit 98e753a6e51b255d474c4db5e7af8b01633b6a4c)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 hw/i386/pc.c         | 9 ++++-----

 hw/i386/pc_piix.c    | 1 +

 hw/i386/pc_q35.c     | 1 +

 include/hw/i386/pc.h | 7 +++----

 4 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c

index 1a0e672..3596de0 100644

--- a/hw/i386/pc.c

+++ b/hw/i386/pc.c

@@ -1048,12 +1048,10 @@ static void load_linux(PCMachineState *pcms,

     fw_cfg_add_i32(fw_cfg, FW_CFG_SETUP_SIZE, setup_size);

     fw_cfg_add_bytes(fw_cfg, FW_CFG_SETUP_DATA, setup, setup_size);

-    if (fw_cfg_dma_enabled(fw_cfg)) {

+    option_rom[nb_option_roms].bootindex = 0;

+    option_rom[nb_option_roms].name = "linuxboot.bin";

+    if (pcmc->linuxboot_dma_enabled && fw_cfg_dma_enabled(fw_cfg)) {

         option_rom[nb_option_roms].name = "linuxboot_dma.bin";

-        option_rom[nb_option_roms].bootindex = 0;

-    } else {

-        option_rom[nb_option_roms].name = "linuxboot.bin";

-        option_rom[nb_option_roms].bootindex = 0;

     }

     nb_option_roms++;

 }

@@ -2327,6 +2325,7 @@ static void pc_machine_class_init(ObjectClass *oc, void *data)

      * to be used at the moment, 32K should be enough for a while.  */

     pcmc->acpi_data_size = 0x20000 + 0x8000;

     pcmc->save_tsc_khz = true;

+    pcmc->linuxboot_dma_enabled = true;

     mc->get_hotplug_handler = pc_get_hotpug_handler;

     mc->cpu_index_to_socket_id = pc_cpu_index_to_socket_id;

     mc->possible_cpu_arch_ids = pc_possible_cpu_arch_ids;

diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c

index fa41189..bbdf2a8 100644

--- a/hw/i386/pc_piix.c

+++ b/hw/i386/pc_piix.c

@@ -476,6 +476,7 @@ static void pc_i440fx_2_6_machine_options(MachineClass *m)

     PCMachineClass *pcmc = PC_MACHINE_CLASS(m);

     pc_i440fx_2_7_machine_options(m);

     pcmc->legacy_cpu_hotplug = true;

+    pcmc->linuxboot_dma_enabled = false;

     SET_MACHINE_COMPAT(m, PC_COMPAT_2_6);

 }

diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c

index 23d5f6b..aad1ae7 100644

--- a/hw/i386/pc_q35.c

+++ b/hw/i386/pc_q35.c

@@ -337,6 +337,7 @@ static void pc_q35_2_6_machine_options(MachineClass *m)

     PCMachineClass *pcmc = PC_MACHINE_CLASS(m);

     pc_q35_2_7_machine_options(m);

     pcmc->legacy_cpu_hotplug = true;

+    pcmc->linuxboot_dma_enabled = false;

     SET_MACHINE_COMPAT(m, PC_COMPAT_2_6);

 }

diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h

index 62ac914..e05d838 100644

--- a/include/hw/i386/pc.h

+++ b/include/hw/i386/pc.h

@@ -151,6 +151,9 @@ struct PCMachineClass {

     bool save_tsc_khz;

     /* generate legacy CPU hotplug AML */

     bool legacy_cpu_hotplug;

+

+    /* use DMA capable linuxboot option rom */

+    bool linuxboot_dma_enabled;

 };

 #define TYPE_PC_MACHINE "generic-pc-machine"

@@ -432,10 +435,6 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);

 #define PC_COMPAT_2_6 \

     HW_COMPAT_2_6 \

     {\

-        .driver   = "fw_cfg_io",\

-        .property = "dma_enabled",\

-        .value    = "off",\

-    },{\

         .driver   = TYPE_X86_CPU,\

         .property = "cpuid-0xb",\

         .value    = "off",\

-- 

1.8.3.1