target/i386: Call accel-agnostic x86_cpu_get_supported_cpuid()

x86_cpu_get_supported_cpuid() is generic and handles the different
accelerators. Use it instead of kvm_arch_get_supported_cpuid().

That fixes a link failure introduced by commit 3adce820
("target/i386: Remove unused KVM stubs") when QEMU is configured
as:

  $ ./configure --cc=clang \
    --target-list=x86_64-linux-user,x86_64-softmmu \
    --enable-debug

We were getting:

  [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.

For the record, this is because '--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 (see commit 2140cfa5 "i386: Fix build by
providing stub kvm_arch_get_supported_cpuid()").

Cc: qemu-stable@nongnu.org
Fixes: 3adce820 ("target/i386: Remove unused KVM stubs")
Reported-by: Kevin Wolf <kwolf@redhat.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20230913093009.83520-4-philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>