On Fri, 09 Nov 2018 01:00:08 PST (-0800), Christoph Hellwig wrote:
These days architectures are mostly out of the business of dealing with struct scatterlist at all, unless they have architecture specific iommu drivers. Replace the ARCH_HAS_SG_CHAIN symbol with a ARCH_NO_SG_CHAIN one only enabled for architectures with horrible legacy iommu drivers like alpha and parisc, and conditionally for arm which wants to keep it disable for legacy platforms. Signed-off-by: Christoph Hellwig <hch@xxxxxx> --- .../features/io/sg-chain/arch-support.txt | 33 ------------------- arch/alpha/Kconfig | 1 + arch/arc/Kconfig | 1 - arch/arm/Kconfig | 2 +- arch/arm64/Kconfig | 1 - arch/ia64/Kconfig | 1 - arch/parisc/Kconfig | 1 + arch/powerpc/Kconfig | 1 - arch/s390/Kconfig | 1 - arch/sparc/Kconfig | 1 - arch/x86/Kconfig | 1 - arch/xtensa/Kconfig | 1 - include/linux/scatterlist.h | 6 ++-- lib/Kconfig | 2 +- lib/scatterlist.c | 2 +- 15 files changed, 8 insertions(+), 47 deletions(-) delete mode 100644 Documentation/features/io/sg-chain/arch-support.txt
As far as I can tell, it looks like m68k, mips, and powerpc mention an IOMMU in their ports, don't set ARCH_HAS_SG_CHAIN, and with this patch set won't set ARCH_NO_SG_CHAIN. The issue is that I'm not sure how to determine what constitutes a horrible legacy IOMMU, at least with respect to not being able to use scatterlist chaining.
I poked through the 68k stuff (sun3 and sun3x) and the only thing I see that's odd is that DVMA_PAGE_SHIFT is 13. That matches PAGE_SHIFT for the subarch, though, so I don't think it's an issue. It looks like the mention in MIPS is trivial, so that should be fine. There's a lot in the PC port so I just glanced at it. I assume it's OK, but I did see an explicit mention of SG in their generic IOMMU. There's a lot of flavors here so I'm not sure how well they all work.
I don't really think that's enough for my reviewed-by tag, so feel free to give me some pointers if you're looking for one -- I'd be happy to lean about IOMMUs (particularly broken ones, as that might help prevent us from designing a broken one), I'm just not sure what I'm looking for.
I'm going to assume you're going to merge this and I'll drop the RISC-V patch that turns on ARCH_HAS_SG_CHAIN.
Thanks!
diff --git a/Documentation/features/io/sg-chain/arch-support.txt b/Documentation/features/io/sg-chain/arch-support.txt deleted file mode 100644 index 6554f0372c3f..000000000000 --- a/Documentation/features/io/sg-chain/arch-support.txt +++ /dev/null @@ -1,33 +0,0 @@ -# -# Feature name: sg-chain -# Kconfig: ARCH_HAS_SG_CHAIN -# description: arch supports chained scatter-gather lists -# - ----------------------- - | arch |status| - ----------------------- - | alpha: | TODO | - | arc: | ok | - | arm: | ok | - | arm64: | ok | - | c6x: | TODO | - | h8300: | TODO | - | hexagon: | TODO | - | ia64: | ok | - | m68k: | TODO | - | microblaze: | TODO | - | mips: | TODO | - | nds32: | TODO | - | nios2: | TODO | - | openrisc: | TODO | - | parisc: | TODO | - | powerpc: | ok | - | riscv: | TODO | - | s390: | ok | - | sh: | TODO | - | sparc: | ok | - | um: | TODO | - | unicore32: | TODO | - | x86: | ok | - | xtensa: | TODO | - ----------------------- diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig index 5b4f88363453..a7e748a46c18 100644 --- a/arch/alpha/Kconfig +++ b/arch/alpha/Kconfig @@ -5,6 +5,7 @@ config ALPHA select ARCH_MIGHT_HAVE_PC_PARPORT select ARCH_MIGHT_HAVE_PC_SERIO select ARCH_NO_PREEMPT + select ARCH_NO_SG_CHAIN select ARCH_USE_CMPXCHG_LOCKREF select HAVE_AOUT select HAVE_IDE diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig index c9e2a1323536..fd48d698da29 100644 --- a/arch/arc/Kconfig +++ b/arch/arc/Kconfig @@ -13,7 +13,6 @@ config ARC select ARCH_HAS_PTE_SPECIAL select ARCH_HAS_SYNC_DMA_FOR_CPU select ARCH_HAS_SYNC_DMA_FOR_DEVICE - select ARCH_HAS_SG_CHAIN select ARCH_SUPPORTS_ATOMIC_RMW if ARC_HAS_LLSC select BUILDTIME_EXTABLE_SORT select CLONE_BACKWARDS diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 91be74d8df65..199eb62230b0 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -19,6 +19,7 @@ config ARM select ARCH_HAVE_CUSTOM_GPIO_H select ARCH_HAS_GCOV_PROFILE_ALL select ARCH_MIGHT_HAVE_PC_PARPORT + select ARCH_NO_SG_CHAIN if !ARM_HAS_SG_CHAIN select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if CPU_V7 select ARCH_SUPPORTS_ATOMIC_RMW @@ -118,7 +119,6 @@ config ARM <http://www.arm.linux.org.uk/>. config ARM_HAS_SG_CHAIN - select ARCH_HAS_SG_CHAIN bool config ARM_DMA_USE_IOMMU diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 787d7850e064..4c851b3a7b7c 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -23,7 +23,6 @@ config ARM64 select ARCH_HAS_MEMBARRIER_SYNC_CORE select ARCH_HAS_PTE_SPECIAL select ARCH_HAS_SET_MEMORY - select ARCH_HAS_SG_CHAIN select ARCH_HAS_STRICT_KERNEL_RWX select ARCH_HAS_STRICT_MODULE_RWX select ARCH_HAS_SYNC_DMA_FOR_DEVICE diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig index 36773def6920..d6f203658994 100644 --- a/arch/ia64/Kconfig +++ b/arch/ia64/Kconfig @@ -29,7 +29,6 @@ config IA64 select HAVE_MEMBLOCK_NODE_MAP select HAVE_VIRT_CPU_ACCOUNTING select ARCH_HAS_DMA_MARK_CLEAN - select ARCH_HAS_SG_CHAIN select VIRT_TO_BUS select ARCH_DISCARD_MEMBLOCK select GENERIC_IRQ_PROBE diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig index 92a339ee28b3..428ee50fc3db 100644 --- a/arch/parisc/Kconfig +++ b/arch/parisc/Kconfig @@ -11,6 +11,7 @@ config PARISC select ARCH_HAS_ELF_RANDOMIZE select ARCH_HAS_STRICT_KERNEL_RWX select ARCH_HAS_UBSAN_SANITIZE_ALL + select ARCH_NO_SG_CHAIN select ARCH_SUPPORTS_MEMORY_FAILURE select RTC_CLASS select RTC_DRV_GENERIC diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 8be31261aec8..4bc8edd83cee 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -138,7 +138,6 @@ config PPC select ARCH_HAS_PTE_SPECIAL select ARCH_HAS_MEMBARRIER_CALLBACKS select ARCH_HAS_SCALED_CPUTIME if VIRT_CPU_ACCOUNTING_NATIVE && PPC64 - select ARCH_HAS_SG_CHAIN select ARCH_HAS_STRICT_KERNEL_RWX if ((PPC_BOOK3S_64 || PPC32) && !RELOCATABLE && !HIBERNATION) select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST select ARCH_HAS_UACCESS_FLUSHCACHE if PPC64 diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 5173366af8f3..5624e8607054 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -73,7 +73,6 @@ config S390 select ARCH_HAS_KCOV select ARCH_HAS_PTE_SPECIAL select ARCH_HAS_SET_MEMORY - select ARCH_HAS_SG_CHAIN select ARCH_HAS_STRICT_KERNEL_RWX select ARCH_HAS_STRICT_MODULE_RWX select ARCH_HAS_UBSAN_SANITIZE_ALL diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig index 490b2c95c212..8853b6ceae17 100644 --- a/arch/sparc/Kconfig +++ b/arch/sparc/Kconfig @@ -40,7 +40,6 @@ config SPARC select MODULES_USE_ELF_RELA select ODD_RT_SIGACTION select OLD_SIGSUSPEND - select ARCH_HAS_SG_CHAIN select CPU_NO_EFFICIENT_FFS select LOCKDEP_SMALL if LOCKDEP select NEED_DMA_MAP_STATE diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index ba7e3464ee92..6faab6f9b57e 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -66,7 +66,6 @@ config X86 select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64 select ARCH_HAS_UACCESS_MCSAFE if X86_64 && X86_MCE select ARCH_HAS_SET_MEMORY - select ARCH_HAS_SG_CHAIN select ARCH_HAS_STRICT_KERNEL_RWX select ARCH_HAS_STRICT_MODULE_RWX select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig index d29b7365da8d..e3387919eb22 100644 --- a/arch/xtensa/Kconfig +++ b/arch/xtensa/Kconfig @@ -1,7 +1,6 @@ # SPDX-License-Identifier: GPL-2.0 config XTENSA def_bool y - select ARCH_HAS_SG_CHAIN select ARCH_HAS_SYNC_DMA_FOR_CPU select ARCH_HAS_SYNC_DMA_FOR_DEVICE select ARCH_NO_COHERENT_DMA_MMAP if !MMU diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 093aa57120b0..b96f0d0b5b8f 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -324,10 +324,10 @@ size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents, * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit * is totally arbitrary, a setting of 2048 will get you at least 8mb ios. */ -#ifdef CONFIG_ARCH_HAS_SG_CHAIN -#define SG_MAX_SEGMENTS 2048 -#else +#ifdef CONFIG_ARCH_NO_SG_CHAIN #define SG_MAX_SEGMENTS SG_CHUNK_SIZE +#else +#define SG_MAX_SEGMENTS 2048 #endif #ifdef CONFIG_SG_POOL diff --git a/lib/Kconfig b/lib/Kconfig index a9965f4af4dd..d5a5e2ebf286 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -577,7 +577,7 @@ config SG_POOL # sg chaining option # -config ARCH_HAS_SG_CHAIN +config ARCH_NO_SG_CHAIN def_bool n config ARCH_HAS_PMEM_API diff --git a/lib/scatterlist.c b/lib/scatterlist.c index 7c6096a71704..9ba349e775ef 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -271,7 +271,7 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents, if (nents == 0) return -EINVAL; -#ifndef CONFIG_ARCH_HAS_SG_CHAIN +#ifdef CONFIG_ARCH_NO_SG_CHAIN if (WARN_ON_ONCE(nents > max_ents)) return -EINVAL; #endif
