| Message ID | 20230911142729.25548-1-philmd@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] target/i386: Restrict system-specific features from user emulation | expand |
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru> Thank you for patience! 11.09.2023 17:27, Philippe Mathieu-Daudé: > 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 ...
Am 11.09.2023 um 16:27 hat Philippe Mathieu-Daudé geschrieben: > 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@redhat.com> > Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org> Can we make the function declarations in the header file for the functions without stubs conditional on !CONFIG_USER_ONLY, too, so that trying to call them would already fail during compilation (and also with -O2), not only when linking without optimisations? Kevin
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)
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@redhat.com> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org> --- target/i386/cpu.c | 4 ++++ 1 file changed, 4 insertions(+)