Control: tags -1 + moreinfo Hi Francesco,
On Sat, Oct 11, 2025 at 06:50:06PM +0200, Francesco Poli wrote: > On Sat, 11 Oct 2025 17:20:36 +0200 Salvatore Bonaccorso wrote: > > > Hi Francesco, > > > > Sorry the delay, busy with other things. > > No problem, it can happen... > > > > > On Sun, Oct 05, 2025 at 09:19:07PM +0200, Francesco Poli wrote: > [...] > > > How do I use gcc-14 to build the Linux kernel? > > > > > > Is > > > > > > $ CC=gcc-14 make -j 2 bindeb-pkg > > > > > > enough? > > > > Pass it actually to make as argument, so: > > > > make CC=gcc-14 -j 2 bindeb-pkg > > > > should do the trick. > > Yes, I searched the web and figured out by myself. > I tried to do so (by passing CC=gcc-14 as argument to each and every > 'make' command, since I was not sure whether it was need for > configuration steps too) and it successfully built .deb packages for > v6.12 > > > > > Let me know if that works to get your bisect running. > > Well, I also built and tested v6.13-rc6 and found an interesting and > unexpected result: v6.13-rc6 is "good", too!!! > > Since I could not believe my eyes (well, actually, my ears), I again > installed and tested 6.13~rc6-1~exp1 from snapshot.debian.org: it is > "bad"! > > > So, let's summarize the situation: > > • if I install Debian kernels from snapshot.debian.org, I get the > following results > > 6.13~rc6-1~exp1 BAD > 6.12.43-1 good > 6.12.41-1 good > 6.12.38-1 good > > • if I build upstream kernels from the git repository, I get the > following results > > # aptitude install flex bison > # aptitude install bc libelf-dev libssl-dev pahole > > $ git clone > https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git > $ cd linux-stable > $ git checkout v6.12 > $ uname -r > 6.12.38+deb13-amd64 > $ cp /boot/config-$(uname -r) .config > $ yes '' | make CC=gcc-14 localmodconfig > $ make CC=gcc-14 savedefconfig > $ mv defconfig arch/x86/configs/my_defconfig > > $ make CC=gcc-14 my_defconfig > $ make CC=gcc-14 -j 3 bindeb-pkg > ---------> v6.12 is good > > $ git checkout v6.13-rc6 > $ make CC=gcc-14 my_defconfig > $ make CC=gcc-14 -j 4 bindeb-pkg > ---------> v6.13-rc6 is good (which is unexpected!) > > > > What should we deduce from this unexpected result? > > Could it be that I built v6.13-rc6 with the '.config' file copied from > '/boot/config-6.12.38+deb13-amd64' ? > Should I try with the '.config' file copied from > '/boot/config-6.16.9+deb14-amd64', instead? > > Or could the issue be in one of the Debian patches (that create source > differences between the Debian kernel > 'linux-image-6.13-rc6-amd64-unsigned' and the upstream kernel > 'linux-image-6.13.0-rc6_6.13.0-rc6-5_amd64.deb', that I rebuilt on my > own)? > > Anything else? > > > What do you suggest to do, next? The suspsect is that you see difference as you end in the self compiled kernel without enabled IOMMU. (Background; The Debian config has CONFIG_INTEL_IOMMU_DEFAULT_ON_INTGPU_OFF=y, ntoably this option does not exist in upstream, so you end with CONFIG_INTEL_IOMMU_DEFAULT_ON not set only and see the difference. (if you want to look up what I'm talking, this is features/x86/intel-iommu-add-kconfig-option-to-exclude-igpu-by-default.patch in the source). before we might suggest you need to use the workaround to disable iommu, can you please now test the *selfcompiled* v6.13-rc6 with IOMMU enabled, by booting it with the kernel command line argument intel_iommu=on. I expect you will see then the problem in same way. Regards, Salvatore
