[PATCH] acpi: Add Windows ACPI Emulated Device Table (WAET)

[Liran Alon]

From: Elad Gabay <address@hidden>

Microsoft introduced this ACPI table to avoid Windows guests performing
various workarounds for device erratas. As the virtual device emulated
by VMM may not have the errata.

Currently, WAET allows hypervisor to inform guest about two
specific behaviors: One for RTC and the other for ACPI PM Timer.

Support for WAET have been introduced since Windows Vista. This ACPI
table is also exposed by other hypervisors, such as VMware, by default.

This patch adds WAET ACPI Table to QEMU. It also makes sure to introduce
the new ACPI table only for new machine-types.

Signed-off-by: Elad Gabay <address@hidden>
Co-developed-by: Liran Alon <address@hidden>
Signed-off-by: Liran Alon <address@hidden>
---
 hw/i386/acpi-build.c        | 18 ++++++++++++++++++
 hw/i386/pc_piix.c           |  2 ++
 hw/i386/pc_q35.c            |  2 ++
 include/hw/acpi/acpi-defs.h | 25 +++++++++++++++++++++++++
 include/hw/i386/pc.h        |  1 +
 5 files changed, 48 insertions(+)

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 9c4e46fa7466..29f70741cd96 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -2512,6 +2512,19 @@ build_dmar_q35(GArray *table_data, BIOSLinker *linker)
     build_header(linker, table_data, (void *)(table_data->data + dmar_start),
                  "DMAR", table_data->len - dmar_start, 1, NULL, NULL);
 }
+
+static void
+build_waet(GArray *table_data, BIOSLinker *linker)
+{
+    AcpiTableWaet *waet;
+
+    waet = acpi_data_push(table_data, sizeof(*waet));
+    waet->emulated_device_flags = cpu_to_le32(ACPI_WAET_PM_TIMER_GOOD);
+
+    build_header(linker, table_data,
+                 (void *)waet, "WAET", sizeof(*waet), 1, NULL, NULL);
+}
+
 /*
  *   IVRS table as specified in AMD IOMMU Specification v2.62, Section 5.2
  *   accessible here http://support.amd.com/TechDocs/48882_IOMMU.pdf
@@ -2859,6 +2872,11 @@ void acpi_build(AcpiBuildTables *tables, MachineState 
*machine)
                           machine->nvdimms_state, machine->ram_slots);
     }
 
+    if (!pcmc->do_not_add_waet_acpi) {
+        acpi_add_table(table_offsets, tables_blob);
+        build_waet(tables_blob, tables->linker);
+    }
+
     /* Add tables supplied by user (if any) */
     for (u = acpi_table_first(); u; u = acpi_table_next(u)) {
         unsigned len = acpi_table_len(u);
diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index 9088db8fb601..2d11a8b50a9c 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -432,9 +432,11 @@ DEFINE_I440FX_MACHINE(v5_0, "pc-i440fx-5.0", NULL,
 
 static void pc_i440fx_4_2_machine_options(MachineClass *m)
 {
+    PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
     pc_i440fx_5_0_machine_options(m);
     m->alias = NULL;
     m->is_default = false;
+    pcmc->do_not_add_waet_acpi = true;
     compat_props_add(m->compat_props, hw_compat_4_2, hw_compat_4_2_len);
     compat_props_add(m->compat_props, pc_compat_4_2, pc_compat_4_2_len);
 }
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index 84cf925cf43a..1e0a726b27a7 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -361,8 +361,10 @@ DEFINE_Q35_MACHINE(v5_0, "pc-q35-5.0", NULL,
 
 static void pc_q35_4_2_machine_options(MachineClass *m)
 {
+    PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
     pc_q35_5_0_machine_options(m);
     m->alias = NULL;
+    pcmc->do_not_add_waet_acpi = true;
     compat_props_add(m->compat_props, hw_compat_4_2, hw_compat_4_2_len);
     compat_props_add(m->compat_props, pc_compat_4_2, pc_compat_4_2_len);
 }
diff --git a/include/hw/acpi/acpi-defs.h b/include/hw/acpi/acpi-defs.h
index 57a3f58b0c9a..803c904471d5 100644
--- a/include/hw/acpi/acpi-defs.h
+++ b/include/hw/acpi/acpi-defs.h
@@ -634,4 +634,29 @@ struct AcpiIortRC {
 } QEMU_PACKED;
 typedef struct AcpiIortRC AcpiIortRC;
 
+/*
+ * Windows ACPI Emulated Devices Table.
+ * Specification:
+ * 
http://download.microsoft.com/download/7/E/7/7E7662CF-CBEA-470B-A97E-CE7CE0D98DC2/WAET.docx
+ */
+
+/*
+ * Indicates whether the RTC has been enhanced not to require acknowledgment
+ * after it asserts an interrupt. With this bit set, an interrupt handler can
+ * bypass reading the RTC register C to unlatch the pending interrupt.
+ */
+#define ACPI_WAET_RTC_GOOD      (1 << 0)
+/*
+ * Indicates whether the ACPI PM timer has been enhanced not to require
+ * multiple reads. With this bit set, only one read of the ACPI PM timer is
+ * necessary to obtain a reliable value.
+ */
+#define ACPI_WAET_PM_TIMER_GOOD (1 << 1)
+
+struct AcpiTableWaet {
+    ACPI_TABLE_HEADER_DEF
+    uint32_t emulated_device_flags;
+} QEMU_PACKED;
+typedef struct AcpiTableWaet AcpiTableWaet;
+
 #endif
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 60c988c4a5aa..f1f64e8f45c8 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -100,6 +100,7 @@ typedef struct PCMachineClass {
     int legacy_acpi_table_size;
     unsigned acpi_data_size;
     bool do_not_add_smb_acpi;
+    bool do_not_add_waet_acpi;
 
     /* SMBIOS compat: */
     bool smbios_defaults;
-- 
2.20.1