From 3c25dd23dd3a83072352685e1fdc00c9f0eb052b Mon Sep 17 00:00:00 2001
From: Igor Mammedov <imammedo@redhat.com>
Date: Mon, 8 Jun 2015 00:52:04 +0200
Subject: [PATCH 048/217] acpi: fix "Memory device control fields" register

Message-id: <1433724727-46928-7-git-send-email-imammedo@redhat.com>
Patchwork-id: 65395
O-Subject: [RHEL-7.2 qemu-kvm-rhev PATCH 6/9] acpi: fix "Memory device control fields" register
Bugzilla: 1120706
RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
RH-Acked-by: Andrew Jones <drjones@redhat.com>
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>

From: Zhu Guihua <zhugh.fnst@cn.fujitsu.com>

0 bit in Memory device control fields must be cleared before writing to
register. But now this field isn't cleared when other fields are written.

To solve this bug, This patch fixes UpdateRule to WriteAsZeros in "Memory
device control fields" register.

Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Zhu Guihua <zhugh.fnst@cn.fujitsu.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 660e8ec70065c8b1fd68b2cb137de16d831959f4)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 docs/specs/acpi_mem_hotplug.txt | 5 ++++-
 hw/i386/acpi-build.c            | 2 +-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/docs/specs/acpi_mem_hotplug.txt b/docs/specs/acpi_mem_hotplug.txt
index dcc4808..68daa14 100644
--- a/docs/specs/acpi_mem_hotplug.txt
+++ b/docs/specs/acpi_mem_hotplug.txt
@@ -31,7 +31,10 @@ Memory hot-plug interface (IO port 0xa00-0xa17, 1-4 byte access):
       [0xc-0x13] reserved, writes into it are ignored
       [0x14] Memory device control fields
           bits:
-              0: reserved, OSPM must clear it before writing to register
+              0: reserved, OSPM must clear it before writing to register.
+                 Due to BUG in versions prior 2.4 that field isn't cleared
+                 when other fields are written. Keep it reserved and don't
+                 try to reuse it.
               1: if set to 1 clears device insert event, set by OSPM
                  after it has emitted device check event for the
                  selected memory device
diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 5977a5b..795af4e 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -927,7 +927,7 @@ build_ssdt(GArray *table_data, GArray *linker,
         aml_append(scope, field);
 
         field = aml_field(stringify(MEMORY_HOTPLUG_IO_REGION), aml_byte_acc,
-                          aml_preserve);
+                          aml_write_as_zeros);
         aml_append(field, aml_reserved_field(160 /* bits, Offset(20) */));
         aml_append(field, /* 1 if enabled, read only */
             aml_named_field(stringify(MEMORY_SLOT_ENABLED), 1));
-- 
1.8.3.1