Thank you Marc for figuring out the filtering-out solution! It fixed the build on ChromeOS. I will update the patch and also filter out `-fprofile-use` which will avoid a similar problem with the instrumented PGO in the future. Thanks, Denis On Thu, Oct 13, 2022 at 4:09 AM Marc Zyngier <maz@xxxxxxxxxx> wrote: > > On Tue, 11 Oct 2022 03:15:36 +0100, > Denis Nikitin <denik@xxxxxxxxxxxx> wrote: > > > > On Sat, Oct 8, 2022 at 7:22 PM Marc Zyngier <maz@xxxxxxxxxx> wrote: > > > > > > On Thu, 06 Oct 2022 17:28:17 +0100, > > > Denis Nikitin <denik@xxxxxxxxxxxx> wrote: > > > > > > > > Hi Mark, > > > > > > s/k/c/ > > > > > > > > > > > This problem currently blocks the PGO roll on the ChromeOS kernel and > > > > we need some kind of a solution. > > > > > > I'm sorry, but I don't feel constrained by your internal deadlines. I > > > have my own... > > > > > > > Could you please take a look? > > > > > > I have asked for a reproducer. All I got for an answer is "this is > > > hard". Providing a profiling file would help, for example. > > > > Could you please try the following profile on the 5.15 branch? > > > > $ cat <<EOF > prof.txt > > kvm_pgtable_walk:100:10 > > 2: 5 > > 3: 5 > > 5: 5 > > 6: 5 > > 10: 5 > > 10: _kvm_pgtable_walk:50 > > 5: 5 > > 7: 5 > > 10: 5 > > 13.2: 5 > > 14: 5 > > 16: 5 __kvm_pgtable_walk:5 > > 13: kvm_pgd_page_idx:30 > > 2: __kvm_pgd_page_idx:30 > > 2: 5 > > 3: 5 > > 5: 5 > > 2: kvm_granule_shift:5 > > 3: 5 > > EOF > > > > $ make LLVM=1 ARCH=arm64 KCFLAGS=-fprofile-sample-use=prof.txt -j8 vmlinux > > Thanks, this was helpful, as I was able to reproduce the build failure. > > FWIW, it seems pretty easy to work around by filtering out the > offending option, making it consistent with the mechanism we already > use for tracing and the like. > > I came up with the hack below, which does the trick and is IMHO better > than dropping the section (extra work) or adding the negation of this > option (which depends on the compiler option evaluation order). > > M. > > diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile > index 48f6ae7cc6e6..7df1b6afca7f 100644 > --- a/arch/arm64/kvm/hyp/nvhe/Makefile > +++ b/arch/arm64/kvm/hyp/nvhe/Makefile > @@ -91,7 +91,7 @@ quiet_cmd_hypcopy = HYPCOPY $@ > > # Remove ftrace, Shadow Call Stack, and CFI CFLAGS. > # This is equivalent to the 'notrace', '__noscs', and '__nocfi' annotations. > -KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS) $(CC_FLAGS_CFI), $(KBUILD_CFLAGS)) > +KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS) $(CC_FLAGS_CFI) -fprofile-sample-use=%, $(KBUILD_CFLAGS)) > > # KVM nVHE code is run at a different exception code with a different map, so > # compiler instrumentation that inserts callbacks or checks into the code may > > > -- > Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
