| Message ID | 20230911131507.24943-1-philmd@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] target/i386: Re-introduce few KVM stubs for Clang debug builds | expand |
On 11/9/23 15:15, Philippe Mathieu-Daudé wrote: > Since commits 3adce820cf..ef1cf6890f, 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. > > '--enable-debug' disables optimizations (CFLAGS=-O0). > > While at this (un)optimization level GCC eliminate the > following dead code: > > if (0 && foo()) { > ... > } > > Clang does not. This was previously documented in commit 2140cfa51d > ("i386: Fix build by providing stub kvm_arch_get_supported_cpuid()"). > > Fix by partially reverting those commits, restoring a pair of stubs > for the unoptimized Clang builds. > > Reported-by: Kevin Wolf <kwolf@redhat.com> > Suggested-by: Daniel P. Berrangé <berrange@redhat.com> > Fixes: 3adce820cf ("target/i386: Remove unused KVM stubs") > Fixes: ef1cf6890f ("target/i386: Allow elision of kvm_hv_vpindex_settable()") > Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org> > --- > target/i386/kvm/kvm-stub.c | 31 +++++++++++++++++++++++++++++++ > target/i386/kvm/meson.build | 2 ++ > 2 files changed, 33 insertions(+) > create mode 100644 target/i386/kvm/kvm-stub.c Patch superseded, see v3: https://lore.kernel.org/qemu-devel/20230911142729.25548-1-philmd@linaro.org/
diff --git a/target/i386/kvm/kvm-stub.c b/target/i386/kvm/kvm-stub.c new file mode 100644 index 0000000000..d3d4a238ce --- /dev/null +++ b/target/i386/kvm/kvm-stub.c @@ -0,0 +1,31 @@ +/* + * QEMU KVM x86 specific function stubs + * + * Copyright Linaro Limited 2012 + * + * Author: Peter Maydell <peter.maydell@linaro.org> + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + * + */ +#include "qemu/osdep.h" +#include "cpu.h" +#include "kvm_i386.h" + +#ifndef __OPTIMIZE__ +/* This function is only called inside conditionals which we + * rely on the compiler to optimize out when CONFIG_KVM is not + * defined. + */ +uint32_t kvm_arch_get_supported_cpuid(KVMState *env, uint32_t function, + uint32_t index, int reg) +{ + abort(); +} +#endif + +bool kvm_hv_vpindex_settable(void) +{ + return false; +} diff --git a/target/i386/kvm/meson.build b/target/i386/kvm/meson.build index 5d9174bbb5..40fbde96ca 100644 --- a/target/i386/kvm/meson.build +++ b/target/i386/kvm/meson.build @@ -1,3 +1,5 @@ +i386_ss.add(when: 'CONFIG_KVM', if_false: files('kvm-stub.c')) + i386_softmmu_kvm_ss = ss.source_set() i386_softmmu_kvm_ss.add(files(
Since commits 3adce820cf..ef1cf6890f, 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. '--enable-debug' disables optimizations (CFLAGS=-O0). While at this (un)optimization level GCC eliminate the following dead code: if (0 && foo()) { ... } Clang does not. This was previously documented in commit 2140cfa51d ("i386: Fix build by providing stub kvm_arch_get_supported_cpuid()"). Fix by partially reverting those commits, restoring a pair of stubs for the unoptimized Clang builds. Reported-by: Kevin Wolf <kwolf@redhat.com> Suggested-by: Daniel P. Berrangé <berrange@redhat.com> Fixes: 3adce820cf ("target/i386: Remove unused KVM stubs") Fixes: ef1cf6890f ("target/i386: Allow elision of kvm_hv_vpindex_settable()") Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org> --- target/i386/kvm/kvm-stub.c | 31 +++++++++++++++++++++++++++++++ target/i386/kvm/meson.build | 2 ++ 2 files changed, 33 insertions(+) create mode 100644 target/i386/kvm/kvm-stub.c