[RISC-V] Address last code review comments

Author: yurai007

src/libraries/Common/tests/TestUtilities/System/PlatformDetection.Unix.cs

@@ -309,13 +309,7 @@ private static bool IsQemu()
         {
             if (IsLinux)
             {
-                foreach (DictionaryEntry entry in Environment.GetEnvironmentVariables())
-                {
-                    if (((String)entry.Key).ToUpper() == "DOTNET_RUNNING_UNDER_QEMU")
-                    {
-                        return true;
-                    }
-                }
+                return Environment.GetEnvironmentVariable("DOTNET_RUNNING_UNDER_QEMU") != null;
             }
             return false;
         }

src/libraries/System.Net.Sockets/tests/FunctionalTests/ArgumentValidationTests.cs

@@ -800,7 +800,7 @@ public void Connect_ConnectTwice_NotSupported(int invalidatingAction)
         {
             using (Socket client = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
             {
-                // On Qemu we omit one test case due to: https://gitlab.com/qemu-project/qemu/-/issues/2410
+                // Skip on Qemu due to https://github.com/dotnet/runtime/issues/104542
                 if (PlatformDetection.IsQemuLinux && invalidatingAction == 1)
                 {
                     return;
@@ -838,8 +838,8 @@ public void ConnectAsync_ConnectTwice_NotSupported(int invalidatingAction)
 
             using (Socket client = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
             {
-                // On Qemu we omit one test case due to: https://gitlab.com/qemu-project/qemu/-/issues/2410
-                if (!PlatformDetection.IsNotQemuLinux && invalidatingAction == 1)
+                // Skip on Qemu due to https://github.com/dotnet/runtime/issues/104542
+                if (PlatformDetection.IsQemuLinux && invalidatingAction == 1)
                 {
                     return;
                 }

src/libraries/System.Net.Sockets/tests/FunctionalTests/KeepAliveTest.cs

@@ -121,7 +121,8 @@ public void Socket_KeepAlive_Interval_And_Time()
             }
         }
 
-        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsNotQemuLinux))] // Skip on Qemu due to https://gitlab.com/qemu-project/qemu/-/issues/2390
+        [Fact]
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/104545", typeof(PlatformDetection), nameof(PlatformDetection.IsQemuLinux))]
         public void Socket_Get_KeepAlive_Time_AsByteArray_OptionLengthZero_Failure()
         {
             using (Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
@@ -144,9 +145,9 @@ public void Socket_Get_KeepAlive_Time_AsByteArray_OptionLengthZero_Failure()
         [InlineData(new byte[3] { 0, 0, 0 })]
         public void Socket_Get_KeepAlive_Time_AsByteArray_BufferNullOrTooSmall_Failure(byte[] buffer)
         {
-            if (!PlatformDetection.IsNotQemuLinux && (buffer == null || buffer.Length == 0))
+            if (PlatformDetection.IsQemuLinux && (buffer == null || buffer.Length == 0))
             {
-                // Skip on Qemu due to https://gitlab.com/qemu-project/qemu/-/issues/2390
+                // Skip on Qemu due to https://github.com/dotnet/runtime/issues/104545
                 return;
             }
             using (Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))

src/libraries/System.Net.Sockets/tests/FunctionalTests/SocketOptionNameTest.cs

@@ -15,7 +15,6 @@ namespace System.Net.Sockets.Tests
     public partial class SocketOptionNameTest
     {
         private static bool SocketsReuseUnicastPortSupport => Capability.SocketsReuseUnicastPortSupport().HasValue;
-        private static bool SupportedOnPlatform = PlatformDetection.IsNotWindowsNanoNorServerCore && PlatformDetection.IsNotQemuLinux;
 
         [ConditionalFact(nameof(SocketsReuseUnicastPortSupport))]
         public void ReuseUnicastPort_CreateSocketGetOption()
@@ -51,7 +50,8 @@ public void ReuseUnicastPort_CreateSocketSetOption()
             }
         }
 
-        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsNotQemuLinux))]
+        [Fact]
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/104547", typeof(PlatformDetection), nameof(PlatformDetection.IsQemuLinux))]
         public void MulticastOption_CreateSocketSetGetOption_GroupAndInterfaceIndex_SetSucceeds_GetThrows()
         {
             int interfaceIndex = 0;
@@ -65,7 +65,8 @@ public void MulticastOption_CreateSocketSetGetOption_GroupAndInterfaceIndex_SetS
             }
         }
 
-        [ConditionalFact(nameof(SupportedOnPlatform))] // Skip on Nano: https://github.com/dotnet/runtime/issues/26286 and Qemu
+        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsNotWindowsNanoNorServerCore))] // Skip on Nano: https://github.com/dotnet/runtime/issues/26286
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/104547", typeof(PlatformDetection), nameof(PlatformDetection.IsQemuLinux))]
         public async Task MulticastInterface_Set_AnyInterface_Succeeds()
         {
             // On all platforms, index 0 means "any interface"
@@ -121,9 +122,10 @@ public void MulticastInterface_Set_InvalidIndex_Throws()
             }
         }
 
-        [ConditionalFact(nameof(SupportedOnPlatform))] // Skip on Nano: https://github.com/dotnet/runtime/issues/26286 and Qemu
+        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsNotWindowsNanoNorServerCore))] // Skip on Nano: https://github.com/dotnet/runtime/issues/26286
         [SkipOnPlatform(TestPlatforms.OSX | TestPlatforms.FreeBSD, "Expected behavior is different on OSX or FreeBSD")]
         [ActiveIssue("https://github.com/dotnet/runtime/issues/52124", TestPlatforms.iOS | TestPlatforms.tvOS | TestPlatforms.MacCatalyst)]
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/104547", typeof(PlatformDetection), nameof(PlatformDetection.IsQemuLinux))]
         public async Task MulticastInterface_Set_IPv6_AnyInterface_Succeeds()
         {
             // On all platforms, index 0 means "any interface"