| Message ID | 1459410252-15531-1-git-send-email-pbonzini@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Paolo,
[auto build test WARNING on v4.6-rc1]
[also build test WARNING on next-20160331]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]
url: https://github.com/0day-ci/linux/commits/Paolo-Bonzini/compiler-gcc-disable-ftracer-for-__noclone-functions/20160331-154556
reproduce:
# apt-get install sparse
make ARCH=x86_64 allmodconfig
make C=1 CF=-D__CHECK_ENDIAN__
sparse warnings: (new ones prefixed by >>)
include/linux/compiler.h:232:8: sparse: attribute 'no_sanitize_address': unknown attribute
>> arch/x86/kvm/vmx.c:8610:13: sparse: attribute '__optimize__': unknown attribute
vim +/__optimize__ +8610 arch/x86/kvm/vmx.c
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov 2011-10-05 8594 int i, nr_msrs;
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov 2011-10-05 8595 struct perf_guest_switch_msr *msrs;
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov 2011-10-05 8596
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov 2011-10-05 8597 msrs = perf_guest_get_msrs(&nr_msrs);
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov 2011-10-05 8598
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov 2011-10-05 8599 if (!msrs)
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov 2011-10-05 8600 return;
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov 2011-10-05 8601
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov 2011-10-05 8602 for (i = 0; i < nr_msrs; i++)
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov 2011-10-05 8603 if (msrs[i].host == msrs[i].guest)
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov 2011-10-05 8604 clear_atomic_switch_msr(vmx, msrs[i].msr);
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov 2011-10-05 8605 else
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov 2011-10-05 8606 add_atomic_switch_msr(vmx, msrs[i].msr, msrs[i].guest,
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov 2011-10-05 8607 msrs[i].host);
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov 2011-10-05 8608 }
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov 2011-10-05 8609
a3b5ba49 arch/x86/kvm/vmx.c Lai Jiangshan 2011-02-11 @8610 static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
6aa8b732 drivers/kvm/vmx.c Avi Kivity 2006-12-10 8611 {
a2fa3e9f drivers/kvm/vmx.c Gregory Haskins 2007-07-27 8612 struct vcpu_vmx *vmx = to_vmx(vcpu);
d974baa3 arch/x86/kvm/vmx.c Andy Lutomirski 2014-10-08 8613 unsigned long debugctlmsr, cr4;
104f226b arch/x86/kvm/vmx.c Avi Kivity 2010-11-18 8614
104f226b arch/x86/kvm/vmx.c Avi Kivity 2010-11-18 8615 /* Record the guest's net vcpu time for enforced NMI injections. */
104f226b arch/x86/kvm/vmx.c Avi Kivity 2010-11-18 8616 if (unlikely(!cpu_has_virtual_nmis() && vmx->soft_vnmi_blocked))
104f226b arch/x86/kvm/vmx.c Avi Kivity 2010-11-18 8617 vmx->entry_time = ktime_get();
104f226b arch/x86/kvm/vmx.c Avi Kivity 2010-11-18 8618
:::::: The code at line 8610 was first introduced by commit
:::::: a3b5ba49a8c58d9a578e016523b047467a41e047 KVM: VMX: add the __noclone attribute to vmx_vcpu_run
:::::: TO: Lai Jiangshan <laijs@cn.fujitsu.com>
:::::: CC: Marcelo Tosatti <mtosatti@redhat.com>
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Paolo Bonzini <pbonzini@redhat.com> wrote: > -ftracer can duplicate asm blocks causing compilation to fail in > noclone functions. For example, KVM declares a global variable > in an asm like > > asm("2: ... \n > .pushsection data \n > .global vmx_return \n > vmx_return: .long 2b"); > > and -ftracer causes a double declaration. > > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Michal Marek <mmarek@suse.cz> > Cc: stable@vger.kernel.org > Cc: kvm@vger.kernel.org > Reported-by: Linda Walsh <lkml@tlinx.org> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > include/linux/compiler-gcc.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h > index 22ab246feed3..eeae401a2412 100644 > --- a/include/linux/compiler-gcc.h > +++ b/include/linux/compiler-gcc.h > @@ -199,7 +199,7 @@ > #define unreachable() __builtin_unreachable() > > /* Mark a function definition as prohibited from being cloned. */ > -#define __noclone __attribute__((__noclone__)) > +#define __noclone __attribute__((__noclone__, __optimize__("no-tracer"))) [ Bringing the thread back from the dead for context ] Setting different optimization attributes to certain functions apparently prevents gcc from inlining functions with different “optimizations”. This results in poor compilation - most notably of vmx_vcpu_run() - and causes short functions such as to_vmx() not to be inlined. Regards, Nadav
On 05/05/2018 19:22, Nadav Amit wrote: > Paolo Bonzini <pbonzini@redhat.com> wrote: > >> -ftracer can duplicate asm blocks causing compilation to fail in >> noclone functions. For example, KVM declares a global variable >> in an asm like >> >> asm("2: ... \n >> .pushsection data \n >> .global vmx_return \n >> vmx_return: .long 2b"); >> >> and -ftracer causes a double declaration. >> >> Cc: Andrew Morton <akpm@linux-foundation.org> >> Cc: Michal Marek <mmarek@suse.cz> >> Cc: stable@vger.kernel.org >> Cc: kvm@vger.kernel.org >> Reported-by: Linda Walsh <lkml@tlinx.org> >> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> >> --- >> include/linux/compiler-gcc.h | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h >> index 22ab246feed3..eeae401a2412 100644 >> --- a/include/linux/compiler-gcc.h >> +++ b/include/linux/compiler-gcc.h >> @@ -199,7 +199,7 @@ >> #define unreachable() __builtin_unreachable() >> >> /* Mark a function definition as prohibited from being cloned. */ >> -#define __noclone __attribute__((__noclone__)) >> +#define __noclone __attribute__((__noclone__, __optimize__("no-tracer"))) > > [ Bringing the thread back from the dead for context ] > > Setting different optimization attributes to certain functions apparently > prevents gcc from inlining functions with different “optimizations”. This > results in poor compilation - most notably of vmx_vcpu_run() - and causes > short functions such as to_vmx() not to be inlined. Hmm, I suppose we need to disable -fno-tracer globally... Has this changed in recent versions of GCC? Paolo
Paolo Bonzini <pbonzini@redhat.com> wrote: > On 05/05/2018 19:22, Nadav Amit wrote: >> Paolo Bonzini <pbonzini@redhat.com> wrote: >> >>> -ftracer can duplicate asm blocks causing compilation to fail in >>> noclone functions. For example, KVM declares a global variable >>> in an asm like >>> >>> asm("2: ... \n >>> .pushsection data \n >>> .global vmx_return \n >>> vmx_return: .long 2b"); >>> >>> and -ftracer causes a double declaration. >>> >>> Cc: Andrew Morton <akpm@linux-foundation.org> >>> Cc: Michal Marek <mmarek@suse.cz> >>> Cc: stable@vger.kernel.org >>> Cc: kvm@vger.kernel.org >>> Reported-by: Linda Walsh <lkml@tlinx.org> >>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> >>> --- >>> include/linux/compiler-gcc.h | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h >>> index 22ab246feed3..eeae401a2412 100644 >>> --- a/include/linux/compiler-gcc.h >>> +++ b/include/linux/compiler-gcc.h >>> @@ -199,7 +199,7 @@ >>> #define unreachable() __builtin_unreachable() >>> >>> /* Mark a function definition as prohibited from being cloned. */ >>> -#define __noclone __attribute__((__noclone__)) >>> +#define __noclone __attribute__((__noclone__, __optimize__("no-tracer"))) >> >> [ Bringing the thread back from the dead for context ] >> >> Setting different optimization attributes to certain functions apparently >> prevents gcc from inlining functions with different “optimizations”. This >> results in poor compilation - most notably of vmx_vcpu_run() - and causes >> short functions such as to_vmx() not to be inlined. > > Hmm, I suppose we need to disable -fno-tracer globally... Has this > changed in recent versions of GCC? I don’t think so. I played with optimization attributes of gcc some time ago and saw the same behavior. Unfortunately, I don’t easily find the place in gcc that implements this behavior.
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index 22ab246feed3..eeae401a2412 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -199,7 +199,7 @@ #define unreachable() __builtin_unreachable() /* Mark a function definition as prohibited from being cloned. */ -#define __noclone __attribute__((__noclone__)) +#define __noclone __attribute__((__noclone__, __optimize__("no-tracer"))) #endif /* GCC_VERSION >= 40500 */
-ftracer can duplicate asm blocks causing compilation to fail in noclone functions. For example, KVM declares a global variable in an asm like asm("2: ... \n .pushsection data \n .global vmx_return \n vmx_return: .long 2b"); and -ftracer causes a double declaration. Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Michal Marek <mmarek@suse.cz> Cc: stable@vger.kernel.org Cc: kvm@vger.kernel.org Reported-by: Linda Walsh <lkml@tlinx.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- include/linux/compiler-gcc.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)