Since commits 3adce820cf ("target/i386: Remove unused KVM
stubs") and ef1cf6890f ("target/i386: Allow elision of
kvm_hv_vpindex_settable()"), when building on a x86 host
configured as:
$ ./configure --cc=clang \
--target-list=x86_64-linux-user,x86_64-softmmu \
--enable-debug
we get:
[71/71] Linking target qemu-x86_64
FAILED: qemu-x86_64
/usr/bin/ld: libqemu-x86_64-linux-user.fa.p/target_i386_cpu.c.o: in function `cpu_x86_cpuid':
cpu.c:(.text+0x1374): undefined reference to `kvm_arch_get_supported_cpuid'
/usr/bin/ld: libqemu-x86_64-linux-user.fa.p/target_i386_cpu.c.o: in function `x86_cpu_filter_features':
cpu.c:(.text+0x81c2): undefined reference to `kvm_arch_get_supported_cpuid'
/usr/bin/ld: cpu.c:(.text+0x81da): undefined reference to `kvm_arch_get_supported_cpuid'
/usr/bin/ld: cpu.c:(.text+0x81f2): undefined reference to `kvm_arch_get_supported_cpuid'
/usr/bin/ld: cpu.c:(.text+0x820a): undefined reference to `kvm_arch_get_supported_cpuid'
/usr/bin/ld: libqemu-x86_64-linux-user.fa.p/target_i386_cpu.c.o:cpu.c:(.text+0x8225): more undefined references to `kvm_arch_get_supported_cpuid' follow
clang: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.
libqemu-x86_64-linux-user.fa is user emulation specific, so
having system emulation code called there is dubious.
'--enable-debug' disables optimizations (CFLAGS=-O0).
While at this (un)optimization level GCC eliminate the
following dead code (CPP output of mentioned build):
static void x86_cpu_get_supported_cpuid(uint32_t func, uint32_t index,
uint32_t *eax, uint32_t *ebx,
uint32_t *ecx, uint32_t *edx)
{
if ((0)) {
*eax = kvm_arch_get_supported_cpuid(kvm_state, func, index, R_EAX);
*ebx = kvm_arch_get_supported_cpuid(kvm_state, func, index, R_EBX);
*ecx = kvm_arch_get_supported_cpuid(kvm_state, func, index, R_ECX);
*edx = kvm_arch_get_supported_cpuid(kvm_state, func, index, R_EDX);
} else if (0) {
*eax = 0;
*ebx = 0;
*ecx = 0;
*edx = 0;
} else {
*eax = 0;
*ebx = 0;
*ecx = 0;
*edx = 0;
}
}
Clang does not.
Instead of trying to deal with compiler specific checks around
__OPTIMIZE__ (see commit 2140cfa51d "i386: Fix build by providing
stub kvm_arch_get_supported_cpuid()"), simply restrict code
belonging to system emulation, easing user emulation linking.
Reported-by: Kevin Wolf <kwolf@xxxxxxxxxx>
Signed-off-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
---
target/i386/cpu.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 24ee67b42d..83914d5d1b 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -6163,6 +6163,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
}
*edx = env->features[FEAT_7_0_EDX]; /* Feature flags */
+#ifndef CONFIG_USER_ONLY
/*
* SGX cannot be emulated in software. If hardware does not
* support enabling SGX and/or SGX flexible launch control,
@@ -6181,6 +6182,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
CPUID_7_0_ECX_SGX_LC))) {
*ecx &= ~CPUID_7_0_ECX_SGX_LC;
}
+#endif
} else if (count == 1) {
*eax = env->features[FEAT_7_1_EAX];
*edx = env->features[FEAT_7_1_EDX];
@@ -7152,6 +7154,7 @@ static void x86_cpu_filter_features(X86CPU *cpu, bool verbose)
mark_unavailable_features(cpu, w, unavailable_features, prefix);
}
+#ifndef CONFIG_USER_ONLY
if ((env->features[FEAT_7_0_EBX] & CPUID_7_0_EBX_INTEL_PT) &&
kvm_enabled()) {
KVMState *s = CPU(cpu)->kvm_state;
@@ -7179,6 +7182,7 @@ static void x86_cpu_filter_features(X86CPU *cpu, bool verbose)
mark_unavailable_features(cpu, FEAT_7_0_EBX, CPUID_7_0_EBX_INTEL_PT, prefix);
}
}
+#endif
}
static void x86_cpu_hyperv_realize(X86CPU *cpu)
--
2.41.0
