acpi/core: always set SCI_EN when SMM isn't supported

If SMM is not supported, ACPI fixed hardware doesn't support
legacy-mode. ACPI-only platform. Where SCI_EN in PM1_CNT register is
always set.
The bit tells OS legacy mode(SCI_EN cleared) or ACPI mode(SCI_EN set).

With the next patch (setting fadt.smi_cmd = 0 when smm isn't enabled),
guest Linux tries to switch to ACPI mode, finds smi_cmd = 0, and then
fails to initialize acpi subsystem. This patch proactively fixes it.

This patch changes guest ABI. To keep compatibility, use
"smm-compat" introduced by earlier patch. If the property is true,
disable new behavior.

ACPI spec 4.8.10.1 PM1 Event Grouping
PM1 Eanble Registers
> For ACPI-only platforms (where SCI_EN is always set)

Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Message-Id: <500f62081626997e46f96377393d3662211763a8.1613615732.git.isaku.yamahata@intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/acpi/core.c

@@ -579,6 +579,10 @@ void acpi_pm1_cnt_update(ACPIREGS *ar,
                          bool sci_enable, bool sci_disable)
 {
     /* ACPI specs 3.0, 4.7.2.5 */
+    if (ar->pm1.cnt.acpi_only) {
+        return;
+    }
+
     if (sci_enable) {
         ar->pm1.cnt.cnt |= ACPI_BITMASK_SCI_ENABLE;
     } else if (sci_disable) {
@@ -608,11 +612,13 @@ static const MemoryRegionOps acpi_pm_cnt_ops = {
 };
 
 void acpi_pm1_cnt_init(ACPIREGS *ar, MemoryRegion *parent,
-                       bool disable_s3, bool disable_s4, uint8_t s4_val)
+                       bool disable_s3, bool disable_s4, uint8_t s4_val,
+                       bool acpi_only)
 {
     FWCfgState *fw_cfg;
 
     ar->pm1.cnt.s4_val = s4_val;
+    ar->pm1.cnt.acpi_only = acpi_only;
     ar->wakeup.notify = acpi_notify_wakeup;
     qemu_register_wakeup_notifier(&ar->wakeup);
 
@@ -638,6 +644,9 @@ void acpi_pm1_cnt_init(ACPIREGS *ar, MemoryRegion *parent,
 void acpi_pm1_cnt_reset(ACPIREGS *ar)
 {
     ar->pm1.cnt.cnt = 0;
+    if (ar->pm1.cnt.acpi_only) {
+        ar->pm1.cnt.cnt |= ACPI_BITMASK_SCI_ENABLE;
+    }
 }
 
 /* ACPI GPE */

hw/acpi/ich9.c

@@ -282,7 +282,7 @@ void ich9_pm_init(PCIDevice *lpc_pci, ICH9LPCPMRegs *pm,
     acpi_pm_tmr_init(&pm->acpi_regs, ich9_pm_update_sci_fn, &pm->io);
     acpi_pm1_evt_init(&pm->acpi_regs, ich9_pm_update_sci_fn, &pm->io);
     acpi_pm1_cnt_init(&pm->acpi_regs, &pm->io, pm->disable_s3, pm->disable_s4,
-                      pm->s4_val);
+                      pm->s4_val, !pm->smm_compat && !smm_enabled);
 
     acpi_gpe_init(&pm->acpi_regs, ICH9_PMIO_GPE0_LEN);
     memory_region_init_io(&pm->io_gpe, OBJECT(lpc_pci), &ich9_gpe_ops, pm,

hw/acpi/piix4.c

@@ -497,7 +497,8 @@ static void piix4_pm_realize(PCIDevice *dev, Error **errp)
 
     acpi_pm_tmr_init(&s->ar, pm_tmr_timer, &s->io);
     acpi_pm1_evt_init(&s->ar, pm_tmr_timer, &s->io);
-    acpi_pm1_cnt_init(&s->ar, &s->io, s->disable_s3, s->disable_s4, s->s4_val);
+    acpi_pm1_cnt_init(&s->ar, &s->io, s->disable_s3, s->disable_s4, s->s4_val,
+                      !s->smm_compat && !s->smm_enabled);
     acpi_gpe_init(&s->ar, GPE_LEN);
 
     s->powerdown_notifier.notify = piix4_pm_powerdown_req;

hw/core/machine.c

@@ -36,7 +36,10 @@
 #include "hw/virtio/virtio.h"
 #include "hw/virtio/virtio-pci.h"
 
-GlobalProperty hw_compat_5_2[] = {};
+GlobalProperty hw_compat_5_2[] = {
+    { "ICH9-LPC", "smm-compat", "on"},
+    { "PIIX4_PM", "smm-compat", "on"},
+};
 const size_t hw_compat_5_2_len = G_N_ELEMENTS(hw_compat_5_2);
 
 GlobalProperty hw_compat_5_1[] = {

hw/isa/vt82c686.c

@@ -190,7 +190,7 @@ static void via_pm_realize(PCIDevice *dev, Error **errp)
 
     acpi_pm_tmr_init(&s->ar, pm_tmr_timer, &s->io);
     acpi_pm1_evt_init(&s->ar, pm_tmr_timer, &s->io);
-    acpi_pm1_cnt_init(&s->ar, &s->io, false, false, 2);
+    acpi_pm1_cnt_init(&s->ar, &s->io, false, false, 2, false);
 }
 
 typedef struct via_pm_init_info {

include/hw/acpi/acpi.h

@@ -128,6 +128,7 @@ struct ACPIPM1CNT {
     MemoryRegion io;
     uint16_t cnt;
     uint8_t s4_val;
+    bool acpi_only;
 };
 
 struct ACPIGPE {
@@ -163,7 +164,8 @@ void acpi_pm1_evt_init(ACPIREGS *ar, acpi_update_sci_fn update_sci,
 
 /* PM1a_CNT: piix and ich9 don't implement PM1b CNT. */
 void acpi_pm1_cnt_init(ACPIREGS *ar, MemoryRegion *parent,
-                       bool disable_s3, bool disable_s4, uint8_t s4_val);
+                       bool disable_s3, bool disable_s4, uint8_t s4_val,
+                       bool acpi_only);
 void acpi_pm1_cnt_update(ACPIREGS *ar,
                          bool sci_enable, bool sci_disable);
 void acpi_pm1_cnt_reset(ACPIREGS *ar);