diff mbox series

[v5,3/6] target/i386: Call accel-agnostic x86_cpu_get_supported_cpuid()

Message ID 20230913093009.83520-4-philmd@linaro.org
State Superseded
Headers show
Series target/i386: Restrict system-specific features from user emulation | expand

Commit Message

Philippe Mathieu-Daudé Sept. 13, 2023, 9:30 a.m. UTC 
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 3adce820cf
("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 2140cfa51d "i386: Fix build by
providing stub kvm_arch_get_supported_cpuid()").

Cc: qemu-stable@nongnu.org
Fixes: 3adce820cf ("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>
---
 target/i386/cpu.c | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

Comments

Michael Tokarev Sept. 13, 2023, 10:59 a.m. UTC | #1 
13.09.2023 12:30, Philippe Mathieu-Daudé:
> 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 3adce820cf
> ("target/i386: Remove unused KVM stubs") when QEMU is configured
> as:
..
> Cc: qemu-stable@nongnu.org
> Fixes: 3adce820cf ("target/i386: Remove unused KVM stubs")

This hopefully should not go to -stable as the issue has been
introduced in v8.1.0-291-g3adce820cf which is past latest release.
That's okay though, - just a small side-note.

/mjt
Philippe Mathieu-Daudé Sept. 13, 2023, 11:01 a.m. UTC | #2 
On 13/9/23 12:59, Michael Tokarev wrote:
> 13.09.2023 12:30, Philippe Mathieu-Daudé:
>> 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 3adce820cf
>> ("target/i386: Remove unused KVM stubs") when QEMU is configured
>> as:
> ..
>> Cc: qemu-stable@nongnu.org
>> Fixes: 3adce820cf ("target/i386: Remove unused KVM stubs")
> 
> This hopefully should not go to -stable as the issue has been
> introduced in v8.1.0-291-g3adce820cf which is past latest release.
> That's okay though, - just a small side-note.

Oh indeed. Paolo, do you mind removing the tag?

Thanks both!
diff mbox series

Patch

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 94b1ba0cf1..b2a20365e1 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -6154,6 +6154,8 @@  void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
     case 7:
         /* Structured Extended Feature Flags Enumeration Leaf */
         if (count == 0) {
+            uint32_t eax_0_unused, ebx_0, ecx_0, edx_0_unused;
+
             /* Maximum ECX value for sub-leaves */
             *eax = env->cpuid_level_func7;
             *ebx = env->features[FEAT_7_0_EBX]; /* Feature flags */
@@ -6168,17 +6170,15 @@  void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
              * support enabling SGX and/or SGX flexible launch control,
              * then we need to update the VM's CPUID values accordingly.
              */
-            if ((*ebx & CPUID_7_0_EBX_SGX) &&
-                (!kvm_enabled() ||
-                 !(kvm_arch_get_supported_cpuid(cs->kvm_state, 0x7, 0, R_EBX) &
-                    CPUID_7_0_EBX_SGX))) {
+            x86_cpu_get_supported_cpuid(0x7, 0,
+                                        &eax_0_unused, &ebx_0,
+                                        &ecx_0, &edx_0_unused);
+            if ((*ebx & CPUID_7_0_EBX_SGX) && !(ebx_0 & CPUID_7_0_EBX_SGX)) {
                 *ebx &= ~CPUID_7_0_EBX_SGX;
             }
 
-            if ((*ecx & CPUID_7_0_ECX_SGX_LC) &&
-                (!(*ebx & CPUID_7_0_EBX_SGX) || !kvm_enabled() ||
-                 !(kvm_arch_get_supported_cpuid(cs->kvm_state, 0x7, 0, R_ECX) &
-                    CPUID_7_0_ECX_SGX_LC))) {
+            if ((*ecx & CPUID_7_0_ECX_SGX_LC)
+                    && (!(*ebx & CPUID_7_0_EBX_SGX) || !(ecx_0 & CPUID_7_0_ECX_SGX_LC))) {
                 *ecx &= ~CPUID_7_0_ECX_SGX_LC;
             }
         } else if (count == 1) {
@@ -7150,14 +7150,14 @@  static void x86_cpu_filter_features(X86CPU *cpu, bool verbose)
         mark_unavailable_features(cpu, w, unavailable_features, prefix);
     }
 
-    if ((env->features[FEAT_7_0_EBX] & CPUID_7_0_EBX_INTEL_PT) &&
-        kvm_enabled()) {
-        KVMState *s = CPU(cpu)->kvm_state;
-        uint32_t eax_0 = kvm_arch_get_supported_cpuid(s, 0x14, 0, R_EAX);
-        uint32_t ebx_0 = kvm_arch_get_supported_cpuid(s, 0x14, 0, R_EBX);
-        uint32_t ecx_0 = kvm_arch_get_supported_cpuid(s, 0x14, 0, R_ECX);
-        uint32_t eax_1 = kvm_arch_get_supported_cpuid(s, 0x14, 1, R_EAX);
-        uint32_t ebx_1 = kvm_arch_get_supported_cpuid(s, 0x14, 1, R_EBX);
+    if (env->features[FEAT_7_0_EBX] & CPUID_7_0_EBX_INTEL_PT) {
+        uint32_t eax_0, ebx_0, ecx_0, edx_0_unused;
+        uint32_t eax_1, ebx_1, ecx_1_unused, edx_1_unused;
+
+        x86_cpu_get_supported_cpuid(0x14, 0,
+                                    &eax_0, &ebx_0, &ecx_0, &edx_0_unused);
+        x86_cpu_get_supported_cpuid(0x14, 1,
+                                    &eax_1, &ebx_1, &ecx_1_unused, &edx_1_unused);
 
         if (!eax_0 ||
            ((ebx_0 & INTEL_PT_MINIMAL_EBX) != INTEL_PT_MINIMAL_EBX) ||