| Message ID | 20260821105609.983622-4-sourabhjain@linux.ibm.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | powerpc: initial support for Kexec HandOver (KHO) | expand |
On Fri, Aug 21 2026, Sourabh Jain wrote: > Enabling CONFIG_KEXEC_HANDOVER together with CONFIG_TRANSPARENT_HUGEPAGE > or CONFIG_HUGETLB_PAGE on powerpc fails to build: > > kernel/liveupdate/kexec_handover.c:49:39: error: expression in static assertion is not constant > 49 | static_assert(SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES); > ./include/linux/build_bug.h:80:56: note: in definition of macro '__static_assert' > 80 | #define __static_assert(expr, msg, ...) _Static_assert(expr, msg) > | ^~~~ > kernel/liveupdate/kexec_handover.c:49:1: note: in expansion of macro 'static_assert' > 49 | static_assert(SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES); > > CMA_MIN_ALIGNMENT_BYTES is derived from pageblock_order, which on > powerpc is not a compile-time constant when THP or HUGETLB_PAGE is > enabled -- powerpc can determine huge page size at runtime in that > configuration, so pageblock_order becomes a variable rather than a > constant expression. KHO's static_assert() on > SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES then fails to > compile, since it requires both sides to be constant expressions. > > Until CMA_MIN_ALIGNMENT_BYTES (or KHO's use of it) is made to handle > the non-constant pageblock_order case on powerpc, exclude > TRANSPARENT_HUGEPAGE and HUGETLB_PAGE from ARCH_SUPPORTS_KEXEC_HANDOVER > so the two can't be enabled together and hit this build failure. This should be a part of patch 2 I think. It is not a good idea to break the build in one patch and fix it in the next. That said, this is a debug check of sorts since SCRATCH_ALIGNMENT_BYTES is of MAX_ORDER_NR_PAGES, and pageblocks _should_ always be smaller of equal to this. Anyway, I don't think this is something you should gate by a config. I think you should either remove the static_assert(), or turn it into a runtime check. +Cc Michal. > > Cc: Aditya Gupta <adityag@linux.ibm.com> > Cc: Alexander Graf <graf@amazon.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Baoquan He <baoquan.he@linux.dev> > Cc: Christophe Leroy (CS GROUP) <chleroy@kernel.org> > Cc: Hari Bathini <hbathini@linux.ibm.com> > Cc: Madhavan Srinivasan <maddy@linux.ibm.com> > Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Mike Rapoport <rppt@kernel.org> > Cc: Nicholas Piggin <npiggin@gmail.com> > Cc: Pasha Tatashin <pasha.tatashin@soleen.com> > Cc: Pratyush Yadav <pratyush@kernel.org> > Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com> > Cc: Shivang Upadhyay <shivangu@linux.ibm.com> > Cc: Shrikanth Hegde <sshegde@linux.ibm.com> > Cc: kexec@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com> > --- > arch/powerpc/Kconfig | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index 61350d3e7a19..f68b9fc883ba 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -720,6 +720,7 @@ config ARCH_SUPPORTS_KEXEC_HANDOVER > def_bool y > depends on PPC64 > depends on !CRASH_DUMP > + depends on !TRANSPARENT_HUGEPAGE && !HUGETLB_PAGE > > config ARCH_SUPPORTS_CRASH_HOTPLUG > def_bool y
On 21/08/26 17:04, Pratyush Yadav wrote: > On Fri, Aug 21 2026, Sourabh Jain wrote: > >> Enabling CONFIG_KEXEC_HANDOVER together with CONFIG_TRANSPARENT_HUGEPAGE >> or CONFIG_HUGETLB_PAGE on powerpc fails to build: >> >> kernel/liveupdate/kexec_handover.c:49:39: error: expression in static assertion is not constant >> 49 | static_assert(SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES); >> ./include/linux/build_bug.h:80:56: note: in definition of macro '__static_assert' >> 80 | #define __static_assert(expr, msg, ...) _Static_assert(expr, msg) >> | ^~~~ >> kernel/liveupdate/kexec_handover.c:49:1: note: in expansion of macro 'static_assert' >> 49 | static_assert(SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES); >> >> CMA_MIN_ALIGNMENT_BYTES is derived from pageblock_order, which on >> powerpc is not a compile-time constant when THP or HUGETLB_PAGE is >> enabled -- powerpc can determine huge page size at runtime in that >> configuration, so pageblock_order becomes a variable rather than a >> constant expression. KHO's static_assert() on >> SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES then fails to >> compile, since it requires both sides to be constant expressions. >> >> Until CMA_MIN_ALIGNMENT_BYTES (or KHO's use of it) is made to handle >> the non-constant pageblock_order case on powerpc, exclude >> TRANSPARENT_HUGEPAGE and HUGETLB_PAGE from ARCH_SUPPORTS_KEXEC_HANDOVER >> so the two can't be enabled together and hit this build failure. > This should be a part of patch 2 I think. It is not a good idea to break > the build in one patch and fix it in the next. Agree. Since this is an RFC patch series, I kept it separate so that this issue could be reviewed independently from patch 2. Going forward, I will merge them. > > That said, this is a debug check of sorts since SCRATCH_ALIGNMENT_BYTES > is of MAX_ORDER_NR_PAGES, and pageblocks _should_ always be smaller of > equal to this. > > Anyway, I don't think this is something you should gate by a config. I > think you should either remove the static_assert(), or turn it into a > runtime check. Agreed. I will evaluate both options and decide which approach makes more sense. Thanks for the review Pratyush. - Sourabh Jain > > +Cc Michal. > >> Cc: Aditya Gupta <adityag@linux.ibm.com> >> Cc: Alexander Graf <graf@amazon.com> >> Cc: Andrew Morton <akpm@linux-foundation.org> >> Cc: Baoquan He <baoquan.he@linux.dev> >> Cc: Christophe Leroy (CS GROUP) <chleroy@kernel.org> >> Cc: Hari Bathini <hbathini@linux.ibm.com> >> Cc: Madhavan Srinivasan <maddy@linux.ibm.com> >> Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com> >> Cc: Michael Ellerman <mpe@ellerman.id.au> >> Cc: Mike Rapoport <rppt@kernel.org> >> Cc: Nicholas Piggin <npiggin@gmail.com> >> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> >> Cc: Pratyush Yadav <pratyush@kernel.org> >> Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com> >> Cc: Shivang Upadhyay <shivangu@linux.ibm.com> >> Cc: Shrikanth Hegde <sshegde@linux.ibm.com> >> Cc: kexec@lists.infradead.org >> Cc: linux-kernel@vger.kernel.org >> Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com> >> --- >> arch/powerpc/Kconfig | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig >> index 61350d3e7a19..f68b9fc883ba 100644 >> --- a/arch/powerpc/Kconfig >> +++ b/arch/powerpc/Kconfig >> @@ -720,6 +720,7 @@ config ARCH_SUPPORTS_KEXEC_HANDOVER >> def_bool y >> depends on PPC64 >> depends on !CRASH_DUMP >> + depends on !TRANSPARENT_HUGEPAGE && !HUGETLB_PAGE >> >> config ARCH_SUPPORTS_CRASH_HOTPLUG >> def_bool y
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 61350d3e7a19..f68b9fc883ba 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -720,6 +720,7 @@ config ARCH_SUPPORTS_KEXEC_HANDOVER def_bool y depends on PPC64 depends on !CRASH_DUMP + depends on !TRANSPARENT_HUGEPAGE && !HUGETLB_PAGE config ARCH_SUPPORTS_CRASH_HOTPLUG def_bool y
Enabling CONFIG_KEXEC_HANDOVER together with CONFIG_TRANSPARENT_HUGEPAGE or CONFIG_HUGETLB_PAGE on powerpc fails to build: kernel/liveupdate/kexec_handover.c:49:39: error: expression in static assertion is not constant 49 | static_assert(SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES); ./include/linux/build_bug.h:80:56: note: in definition of macro '__static_assert' 80 | #define __static_assert(expr, msg, ...) _Static_assert(expr, msg) | ^~~~ kernel/liveupdate/kexec_handover.c:49:1: note: in expansion of macro 'static_assert' 49 | static_assert(SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES); CMA_MIN_ALIGNMENT_BYTES is derived from pageblock_order, which on powerpc is not a compile-time constant when THP or HUGETLB_PAGE is enabled -- powerpc can determine huge page size at runtime in that configuration, so pageblock_order becomes a variable rather than a constant expression. KHO's static_assert() on SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES then fails to compile, since it requires both sides to be constant expressions. Until CMA_MIN_ALIGNMENT_BYTES (or KHO's use of it) is made to handle the non-constant pageblock_order case on powerpc, exclude TRANSPARENT_HUGEPAGE and HUGETLB_PAGE from ARCH_SUPPORTS_KEXEC_HANDOVER so the two can't be enabled together and hit this build failure. Cc: Aditya Gupta <adityag@linux.ibm.com> Cc: Alexander Graf <graf@amazon.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Baoquan He <baoquan.he@linux.dev> Cc: Christophe Leroy (CS GROUP) <chleroy@kernel.org> Cc: Hari Bathini <hbathini@linux.ibm.com> Cc: Madhavan Srinivasan <maddy@linux.ibm.com> Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Mike Rapoport <rppt@kernel.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Pratyush Yadav <pratyush@kernel.org> Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com> Cc: Shivang Upadhyay <shivangu@linux.ibm.com> Cc: Shrikanth Hegde <sshegde@linux.ibm.com> Cc: kexec@lists.infradead.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com> --- arch/powerpc/Kconfig | 1 + 1 file changed, 1 insertion(+)