[PATCH qemu-server v2] query-machine-capabilities: limit AuthenticAMD and GenuineIntel checks to x86-64

[Kaiyang Wu <wukaiyang2003@gmail.com>]

Intel TDX and AMD SEV are both x86-64-only extensions [0] [1]. The current
method of checking results in compilation errors on "unknown" vendors,
where the current placeholder string length ("Unknown") mismatches the
lengths of both "AuthenticAMD" and "GenuineIntel":

    error: ‘strncmp’ of strings of length 7 and 12 and bound of 12
    evaluates to nonzero [-Werror=string-compare]

Limit the machine capability checks for Intel TDX and AMD SEV to x86-64 to
fix build.

[0]: https://docs.kernel.org/arch/x86/tdx.html
[1]: https://docs.kernel.org/virt/kvm/x86/amd-memory-encryption.html

Signed-off-by: Kaiyang Wu <wukaiyang@loongfans.cn>
---

v1: https://lore.proxmox.com/pve-devel/20260603055031.106241-1-wukaiyang@loongfans.cn/

Changes v1 -> v2:
- Use conditional compilation to limit Intel TDX and AMD SEV checks to x86-64
- Eliminate the vendor string length check

 src/query-machine-capabilities/query-machine-capabilities.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/query-machine-capabilities/query-machine-capabilities.c b/src/query-machine-capabilities/query-machine-capabilities.c
index abb47acd..3ccd30da 100644
--- a/src/query-machine-capabilities/query-machine-capabilities.c
+++ b/src/query-machine-capabilities/query-machine-capabilities.c
@@ -204,6 +204,7 @@ int main() {
         eprintf("Error writing to file '" OUTPUT_PATH "': %s\n", strerror(errno));
     }
 
+#ifdef __x86_64__
     if (strncmp(vendor, "AuthenticAMD", 12) == 0) {
         cpu_caps_amd_sev_t caps_sev;
         query_cpu_capabilities_sev(&caps_sev);
@@ -233,7 +234,7 @@ int main() {
             );
         }
     }
-#ifdef __aarch64__
+#elif defined(__aarch64__)
     else {
         cpu_caps_arm_t caps_arm;
         query_cpu_capabilities_arm(&caps_arm);
-- 
2.55.0