Hi Will, On Wed, Jul 12, 2017 at 7:16 PM, Linux Kernel Mailing List <linux-ker...@vger.kernel.org> wrote: > Web: > https://git.kernel.org/torvalds/c/c1004803b40596c1aabbbc78a6b1b33e4dfd96c6 > Commit: c1004803b40596c1aabbbc78a6b1b33e4dfd96c6 > Parent: 58188afeb727e0f73706f1460707bd3ba6ccc221 > Refname: refs/heads/master > Author: Will Deacon <will.dea...@arm.com> > AuthorDate: Fri Jun 23 11:45:57 2017 +0100 > Committer: Will Deacon <will.dea...@arm.com> > CommitDate: Fri Jun 23 17:58:02 2017 +0100 > > iommu/io-pgtable: depend on !GENERIC_ATOMIC64 when using COMPILE_TEST > with LPAE > > The LPAE/ARMv8 page table format relies on the ability to read and write > 64-bit page table entries in an atomic fashion. With the move to a > lockless > implementation, we also need support for cmpxchg64 to resolve races when > installing table entries concurrently. > > Unfortunately, not all architectures support cmpxchg64, so the code can > fail to compiler when building for these architectures using COMPILE_TEST. > Rather than disable COMPILE_TEST altogether, instead check that > GENERIC_ATOMIC64 is not selected, which is a reasonable indication that > the architecture has support for 64-bit cmpxchg. > > Reported-by: kbuild test robot <fengguang...@intel.com> > Signed-off-by: Will Deacon <will.dea...@arm.com> > --- > drivers/iommu/Kconfig | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > index 6ee3a25ae731..c88cfa7522b2 100644 > --- a/drivers/iommu/Kconfig > +++ b/drivers/iommu/Kconfig > @@ -23,7 +23,7 @@ config IOMMU_IO_PGTABLE > config IOMMU_IO_PGTABLE_LPAE > bool "ARMv7/v8 Long Descriptor Format" > select IOMMU_IO_PGTABLE > - depends on HAS_DMA && (ARM || ARM64 || COMPILE_TEST) > + depends on HAS_DMA && (ARM || ARM64 || (COMPILE_TEST && > !GENERIC_ATOMIC64)) > help > Enable support for the ARM long descriptor pagetable format. > This allocator supports 4K/2M/1G, 16K/32M and 64K/512M page
I can't find where this patch was submitted and discussed, so I'm replying to this email. On which architectures did it fail to compile? cmpxchg64() is defined by include/asm-generic/cmpxchg.h, so I fail to see what's the relation with GENERIC_ATOMIC64, which is related to lib/atomic64.c instead. E.g. on m68k, which uses GENERIC_ATOMIC64, it compile-tested fine before. Perhaps there's another (SMP vs UP?) dependency, as include/asm-generic/cmpxchg.h cannot be used on SMP? Should it be COMPILE_TEST && (!GENERIC_ATOMIC64 || !SMP)? Thanks! Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu