acpi_mem_hotplug.txt states that 0 bit in Memory device control fields
must be cleared before writing to register. Now "Memory device control
fields" is declared with "Preserve" update rule, so 0 bit isn't cleared
when other fields are written.
To solve this bug, This patch fixes UpdateRule to WriteAsZeros in "Memory
device control fields" register.
Signed-off-by: Zhu Guihua <zhugh.f...@cn.fujitsu.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 dc1b8e8..eb66fef 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -924,7 +924,7 @@ 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));
--
1.9.3
