On 9/24/24 00:45, Geert Uytterhoeven wrote:
Hi Günter,
CC kbuild
I have two comments...
On Tue, Sep 24, 2024 at 1:52 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
On 9/23/24 15:08, Guenter Roeck wrote:
On 9/23/24 08:23, David Hildenbrand wrote:
On 23.09.24 16:25, Guenter Roeck wrote:
SPLIT_PTE_PTLOCKS already depends on "NR_CPUS >= 4", but that evaluates
to true if there is no NR_CPUS configuration option (such as for m68k).
This results in CONFIG_SPLIT_PTE_PTLOCKS=y for mac_defconfig.
This in turn causes the m68k "q800" machine to crash in qemu.
Should this be fixed in Kconfig (too)?
I don't know. I thought that was intentional, though I don't understand
the logic. I didn't find a documentation that would explain how boolean
dependencies of integer objects are supposed to be handled. My expectation
that it would be similar to C was obviously wrong.
Oh, that's why my compile tests still worked ... I even removed the additional NR_CPUS check, assuming it's not required ...
Thanks for debugging and fixing!
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Apparently it wasn't that simple :-(. 0-day reports a build failure
with s390 builds.
arch/s390/mm/gmap.c:357:16: error: implicit declaration of function 'pmd_pgtable_page'.
Turns out that
depends on NR_CPUS && NR_CPUS >= 4
doesn't work and disables SPLIT_PTE_PTLOCKS even if NR_CPUS _is_ defined.
I have no idea how to declare the dependency correctly.
Sorry, I did not expect that.
The only solution I found was to define NR_CPUS for m68k. That seems to be
the only architecture not defining it, so hopefully that is an acceptable
solution. I'll send v2 of the patch shortly.
My first thought was to agree, as m68k is indeed the only architecture
that does not define NR_CPUS. Upon closer look, most architectures
have NR_CPUS depend on SMP, hence I assume the issue could happen for
those too (although I didn't manage to create such a config on anything
but m68k)? So the simple solution would be to add a dependency on
SMP to SPLIT_PTE_PTLOCKS.
Makes sense. I'll send v3.
Guenter
