[PATCH 2/3] Fix: Reverse CPUs presence check logic for x86 backward compatability

[Salil Mehta via <qemu-devel@nongnu.org>]

Checking `is_present` first can break x86 migration from new Qemu
version to old Qemu. This is because CPRS Bit is not defined in the
older Qemu register block and will always be 0 resulting in check always
failing. Reversing the logic to first check `is_enabled` can alleviate
below problem:

-                If ((\_SB.PCI0.PRES.CPEN == One))
-                {
-                    Local0 = 0x0F
+                If ((\_SB.PCI0.PRES.CPRS == One))
+                {
+                    If ((\_SB.PCI0.PRES.CPEN == One))
+                    {
+                        Local0 = 0x0F
+                    }
+                    Else
+                    {
+                        Local0 = 0x0D
+                    }
                 }

Suggested-by: Igor Mammedov <imammedo@redhat.com>
Message-ID: <20241106100047.18901c9d@imammedo.users.ipa.redhat.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
---
 hw/acpi/cpu.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
index 23443f09a5..b2f7a2b27e 100644
--- a/hw/acpi/cpu.c
+++ b/hw/acpi/cpu.c
@@ -490,22 +490,22 @@ void build_cpus_aml(Aml *table, MachineState *machine, CPUHotplugFeatures opts,
             aml_append(method, aml_acquire(ctrl_lock, 0xFFFF));
             aml_append(method, aml_store(idx, cpu_selector));
             aml_append(method, aml_store(zero, sta));
-            ifctx = aml_if(aml_equal(is_present, one));
+            ifctx = aml_if(aml_equal(is_enabled, one));
             {
-                ifctx2 = aml_if(aml_equal(is_enabled, one));
-                {
-                    /* cpu is present and enabled */
-                    aml_append(ifctx2, aml_store(aml_int(0xF), sta));
-                }
-                aml_append(ifctx, ifctx2);
-                else_ctx = aml_else();
+                /* cpu is present and enabled */
+                aml_append(ifctx, aml_store(aml_int(0xF), sta));
+            }
+            aml_append(method, ifctx);
+            else_ctx = aml_else();
+            {
+                ifctx2 = aml_if(aml_equal(is_present, one));
                 {
                     /* cpu is present but disabled */
-                    aml_append(else_ctx, aml_store(aml_int(0xD), sta));
+                    aml_append(ifctx2, aml_store(aml_int(0xD), sta));
                 }
-                aml_append(ifctx, else_ctx);
+                aml_append(else_ctx, ifctx2);
             }
-            aml_append(method, ifctx);
+            aml_append(method, else_ctx);
             aml_append(method, aml_release(ctrl_lock));
             aml_append(method, aml_return(sta));
         }
-- 
2.34.1