I just updated my kernel from 5.2.14 to 5.3.0. app-emulation/virtualbox-modules-6.0.12 compiled on 5.2.14 but failes on 5.3.0 with almost the same .config (minor changes due to new kernel options).

---- snip ----
test -e include/generated/autoconf.h -a -e include/config/auto.conf || (                \
echo >&2;                                                       \
echo >&2 "  ERROR: Kernel configuration is invalid.";           \
echo >&2 "         include/generated/autoconf.h or include/config/auto.conf are missing.";\
echo >&2 "         Run 'make oldconfig && make prepare' on kernel src to fix it.";      \
echo >&2 ;                                                      \
/bin/false)
---- snip ----

This doesn't seem to be the error stopping the build though.

---- snip ----
…/work/vboxdrv/linux/SUPDrv-linux.o: warning: objtool: VBoxDrvLinuxIOCtl_6_0_12()+0xa4: call to VBoxHost_RTR0MemUserCopyFrom() with UACCESS enabled
…/work/vboxdrv/r0drv/linux/mp-r0drv-linux.c: In function ‘VBoxHost_RTMpOnAll’:
…/work/vboxdrv/r0drv/linux/mp-r0drv-linux.c:287:18: error: void value not ignored as it ought to be
  287 |         int rc = smp_call_function(rtmpLinuxAllWrapper, &Args, 0 /* wait */);
      |                  ^~~~~~~~~~~~~~~~~
…/work/vboxdrv/r0drv/linux/mp-r0drv-linux.c: In function ‘VBoxHost_RTMpOnOthers’:
…/work/vboxdrv/r0drv/linux/mp-r0drv-linux.c:341:8: error: void value not ignored as it ought to be
  341 |     rc = smp_call_function(rtmpLinuxWrapper, &Args, 1 /* wait */);
      |        ^
---- snip ----
make[3]: *** [scripts/Makefile.build:281: …/work/vboxdrv/r0drv/linux/mp-r0drv-linux.o] Error 1
make[3]: *** Waiting for unfinished jobs....
---- snip ----

This stopped the build.