On Thu, Dec 5, 2019 at 11:41 AM Tetsuo Handa
[off-list ref] wrote:

On 2019/12/05 19:22, Paolo Bonzini wrote:

quoted

Ah, and because the machine is a KVM guest, kvm_wait appears in a lot of
backtrace and I get to share syzkaller's joy every time. :)

This bisect result is bogus, though Tetsuo found the bug anyway.
Perhaps you can exclude commits that only touch architectures other than
x86?

It would be nice if coverage functionality can extract filenames in the source
code and supply the list of filenames as arguments for bisect operation.

Also, (unrelated but) it would be nice if we can have "make yes2modconfig"
target which converts CONFIG_FOO=y to CONFIG_FOO=m if FOO is tristate.
syzbot is testing kernel configs close to "make allyesconfig" but I want to
save kernel rebuild time by disabling unrelated functionality when manually
"debug printk()ing" kernels.

I thought that maybe sed "s#=y#=m#g" && make olddefconfig will do, but
unfortunately, it turns off non-tristate configs...

$ egrep "CONFIG_MEMORY_HOTPLUG|CONFIG_TCP_CONG_DCTCP" .config
CONFIG_MEMORY_HOTPLUG=y
CONFIG_TCP_CONG_DCTCP=y
# sed -i "s/CONFIG_MEMORY_HOTPLUG=y/CONFIG_MEMORY_HOTPLUG=m/g" .config
# sed -i "s/CONFIG_TCP_CONG_DCTCP=y/CONFIG_TCP_CONG_DCTCP=m/g" .config
# egrep "CONFIG_MEMORY_HOTPLUG|CONFIG_TCP_CONG_DCTCP" .config
CONFIG_MEMORY_HOTPLUG=m
CONFIG_TCP_CONG_DCTCP=m
# make olddefconfig
# egrep "CONFIG_MEMORY_HOTPLUG|CONFIG_TCP_CONG_DCTCP" .config
# CONFIG_MEMORY_HOTPLUG is not set
CONFIG_TCP_CONG_DCTCP=m