From c835c9faa33909024e343fab0ec93b4ba9c8d06b Mon Sep 17 00:00:00 2001
From: "Bobby R. Bruce" <bbruce@ucdavis.edu>
Date: Wed, 16 Aug 2023 01:17:19 -0500
Subject: [PATCH] arch-x86,cpu-kvm: Fix gem5.fast due to unused variable
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Detected via this failing workload:
https://github.com/gem5/gem5/actions/runs/5861958237

It caused the following compilation error to be thrown:

```
src/arch/x86/kvm/x86_cpu.cc:1462:22: error: unused variable ‘rv’ [-Werror=unused-variable]
 1462 |                 bool rv = isa->cpuid->doCpuid(tc, function, idx, cpuid);
      |                      ^~
```

`rv` is unused in the .fast compilation as it's only used in the
`assert` statement immediately after.

 To fix this, the `[[maybe_unused]]` annotation is used

Change-Id: Ib98dd859c62f171c8eeefae93502f92a8f133776
---
 src/arch/x86/kvm/x86_cpu.cc | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/arch/x86/kvm/x86_cpu.cc b/src/arch/x86/kvm/x86_cpu.cc
index e1c1b0dfc0..b88a96a2b9 100644
--- a/src/arch/x86/kvm/x86_cpu.cc
+++ b/src/arch/x86/kvm/x86_cpu.cc
@@ -1459,7 +1459,8 @@ X86KvmCPU::updateCPUID()
             m5_supported.push_back(makeKvmCpuid(function, idx, cpuid));
         } else {
             while (true) {
-                bool rv = isa->cpuid->doCpuid(tc, function, idx, cpuid);
+                [[maybe_unused]] bool rv = isa->cpuid->doCpuid(
+                    tc, function, idx, cpuid);
                 assert(rv);
 
                 if (idx &&
@@ -1493,7 +1494,8 @@ X86KvmCPU::updateCPUID()
             m5_supported.push_back(makeKvmCpuid(function, idx, cpuid));
         } else {
             while (true) {
-                bool rv = isa->cpuid->doCpuid(tc, function, idx, cpuid);
+                [[maybe_unused]] bool rv = isa->cpuid->doCpuid(
+                    tc, function, idx, cpuid);
                 assert(rv);
 
                 if (idx &&