| Message ID | 20240924154205.1491376-1-linux@roeck-us.net (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] mm: Make SPLIT_PTE_PTLOCKS depend on SMP | expand |
On 24.09.24 17:42, Guenter Roeck wrote: > SPLIT_PTE_PTLOCKS depends on "NR_CPUS >= 4". Unfortunately, that evaluates > to true if there is no NR_CPUS configuration option. This results in > CONFIG_SPLIT_PTE_PTLOCKS=y for mac_defconfig. This in turn causes the m68k > "q800" and "virt" machines to crash in qemu if debugging options are > enabled. > > Making CONFIG_SPLIT_PTE_PTLOCKS dependent on the existence of NR_CPUS > does not work since a dependency on the existence of a numeric Kconfig > entry always evaluates to false. Example: > > config HAVE_NO_NR_CPUS > def_bool y > depends on !NR_CPUS > > After adding this to a Kconfig file, "make defconfig" includes: > $ grep NR_CPUS .config > CONFIG_NR_CPUS=64 > CONFIG_HAVE_NO_NR_CPUS=y > > Defining NR_CPUS for m68k does not help either since many architectures > define NR_CPUS only for SMP configurations. > > Make SPLIT_PTE_PTLOCKS depend on SMP instead to solve the problem. > > Fixes: 394290cba966 ("mm: turn USE_SPLIT_PTE_PTLOCKS / USE_SPLIT_PTE_PTLOCKS into Kconfig options") > Cc: David Hildenbrand <david@redhat.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Geert Uytterhoeven <geert@linux-m68k.org> > Signed-off-by: Guenter Roeck <linux@roeck-us.net> > --- Acked-by: David Hildenbrand <david@redhat.com>
On Tue, Sep 24, 2024 at 5:42 PM Guenter Roeck <linux@roeck-us.net> wrote: > SPLIT_PTE_PTLOCKS depends on "NR_CPUS >= 4". Unfortunately, that evaluates > to true if there is no NR_CPUS configuration option. This results in > CONFIG_SPLIT_PTE_PTLOCKS=y for mac_defconfig. This in turn causes the m68k > "q800" and "virt" machines to crash in qemu if debugging options are > enabled. > > Making CONFIG_SPLIT_PTE_PTLOCKS dependent on the existence of NR_CPUS > does not work since a dependency on the existence of a numeric Kconfig > entry always evaluates to false. Example: > > config HAVE_NO_NR_CPUS > def_bool y > depends on !NR_CPUS > > After adding this to a Kconfig file, "make defconfig" includes: > $ grep NR_CPUS .config > CONFIG_NR_CPUS=64 > CONFIG_HAVE_NO_NR_CPUS=y > > Defining NR_CPUS for m68k does not help either since many architectures > define NR_CPUS only for SMP configurations. > > Make SPLIT_PTE_PTLOCKS depend on SMP instead to solve the problem. > > Fixes: 394290cba966 ("mm: turn USE_SPLIT_PTE_PTLOCKS / USE_SPLIT_PTE_PTLOCKS into Kconfig options") > Cc: David Hildenbrand <david@redhat.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Geert Uytterhoeven <geert@linux-m68k.org> > Signed-off-by: Guenter Roeck <linux@roeck-us.net> Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org> Tested-by: Geert Uytterhoeven <geert@linux-m68k.org> > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -595,6 +595,7 @@ config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE > config SPLIT_PTE_PTLOCKS > def_bool y > depends on MMU > + depends on SMP > depends on NR_CPUS >= 4 Nit: please combine these two lines, to make it clear they are related. > depends on !ARM || CPU_CACHE_VIPT > depends on !PARISC || PA20 Gr{oetje,eeting}s, Geert
diff --git a/mm/Kconfig b/mm/Kconfig index e85164c2812b..33fa51d608dc 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -595,6 +595,7 @@ config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE config SPLIT_PTE_PTLOCKS def_bool y depends on MMU + depends on SMP depends on NR_CPUS >= 4 depends on !ARM || CPU_CACHE_VIPT depends on !PARISC || PA20
SPLIT_PTE_PTLOCKS depends on "NR_CPUS >= 4". Unfortunately, that evaluates to true if there is no NR_CPUS configuration option. This results in CONFIG_SPLIT_PTE_PTLOCKS=y for mac_defconfig. This in turn causes the m68k "q800" and "virt" machines to crash in qemu if debugging options are enabled. Making CONFIG_SPLIT_PTE_PTLOCKS dependent on the existence of NR_CPUS does not work since a dependency on the existence of a numeric Kconfig entry always evaluates to false. Example: config HAVE_NO_NR_CPUS def_bool y depends on !NR_CPUS After adding this to a Kconfig file, "make defconfig" includes: $ grep NR_CPUS .config CONFIG_NR_CPUS=64 CONFIG_HAVE_NO_NR_CPUS=y Defining NR_CPUS for m68k does not help either since many architectures define NR_CPUS only for SMP configurations. Make SPLIT_PTE_PTLOCKS depend on SMP instead to solve the problem. Fixes: 394290cba966 ("mm: turn USE_SPLIT_PTE_PTLOCKS / USE_SPLIT_PTE_PTLOCKS into Kconfig options") Cc: David Hildenbrand <david@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by: Guenter Roeck <linux@roeck-us.net> --- v3: Make SPLIT_PTE_PTLOCKS depend on SMP instead of defining NR_CPUS for m68k. Drop David's Acked-by: tag. v2: Instead of trying to make SPLIT_PTE_PTLOCKS depend on the existence of NR_CPUS, define NR_CPUS for m68k. https://lore.kernel.org/lkml/20240923235617.1584056-1-linux@roeck-us.net/ v1: https://lore.kernel.org/lkml/20240923142533.1197982-1-linux@roeck-us.net/ mm/Kconfig | 1 + 1 file changed, 1 insertion(+)