From 47d833394a09068ba0607a57aa149dfe3dc11e8b Mon Sep 17 00:00:00 2001
From: Iain Buclaw <ibuclaw@gdcproject.org>
Date: Tue, 7 Nov 2023 14:04:07 +0100
Subject: [PATCH] libphobos: Fix regression d21 loops in getCpuInfo0B in
 Solaris/x86 kernel zone

This function assumes that cpuid would return "invalid domain" when a
sub-leaf index greater than what's supported is requested.  This turned
out not to always be the case when running on some virtual machines.

As the loop only does anything for levels 0 and 1, make that a hard
limit for number of times the loop is ran.

    PR d/112408

libphobos/ChangeLog:

	* libdruntime/core/cpuid.d (getCpuInfo0B): Limit number of times loop
	runs.

(cherry picked from commit 0b25c1295d4e84af681f4b1f4af2ad37cd270da3)
---
 libphobos/libdruntime/core/cpuid.d | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/libphobos/libdruntime/core/cpuid.d b/libphobos/libdruntime/core/cpuid.d
index e31f776d7eec..b05db248b816 100644
--- a/libphobos/libdruntime/core/cpuid.d
+++ b/libphobos/libdruntime/core/cpuid.d
@@ -651,10 +651,12 @@ void getAMDcacheinfo()
 // to determine number of processors.
 void getCpuInfo0B()
 {
-    int level=0;
     int threadsPerCore;
     uint a, b, c, d;
-    do {
+    // I'm not sure about this. The docs state that there
+    // are 2 hyperthreads per core if HT is factory enabled.
+    for (int level = 0; level < 2; level++)
+    {
         version (GNU_OR_LDC) asm pure nothrow @nogc {
             "cpuid" : "=a" (a), "=b" (b), "=c" (c), "=d" (d) : "a" (0x0B), "c" (level);
         } else asm pure nothrow @nogc {
@@ -666,19 +668,20 @@ void getCpuInfo0B()
             mov c, ECX;
             mov d, EDX;
         }
-        if (b!=0) {
-           // I'm not sure about this. The docs state that there
-           // are 2 hyperthreads per core if HT is factory enabled.
-            if (level==0)
+        if (b != 0)
+        {
+            if (level == 0)
                 threadsPerCore = b & 0xFFFF;
-            else if (level==1) {
+            else if (level == 1)
+            {
                 cpuFeatures.maxThreads = b & 0xFFFF;
                 cpuFeatures.maxCores = cpuFeatures.maxThreads / threadsPerCore;
             }
-
         }
-        ++level;
-    } while (a!=0 || b!=0);
+        // Got "invalid domain" returned from cpuid
+        if (a == 0 && b == 0)
+            break;
+    }
 }
 
 void cpuidX86()
-- 
2.47.2