| Message ID | 1442479227-18320-1-git-send-email-andre.przywara@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
From: Andre Przywara <andre.przywara@arm.com> Date: Thu, 17 Sep 2015 09:40:27 +0100 > It seems the types used in this file are not really correct, but a > fix isn't trivial. So for the time being restrict this code to be > compiled only when we actually need it. Compile tested on Sparc, > Sparc64, PPC64, ARM, ARM64, x86. The whole reason this code gets compiled unconditionally is to ensure it's portability so that other platforms can use it at some point. So I would ask that, instead of sweeping it under the rug, you help work on fixing the problem you've uncovered. Thanks.
Hi David, On 17/09/15 19:38, David Miller wrote: > From: Andre Przywara <andre.przywara@arm.com> > Date: Thu, 17 Sep 2015 09:40:27 +0100 > >> It seems the types used in this file are not really correct, but a >> fix isn't trivial. So for the time being restrict this code to be >> compiled only when we actually need it. Compile tested on Sparc, >> Sparc64, PPC64, ARM, ARM64, x86. > > The whole reason this code gets compiled unconditionally is to > ensure it's portability so that other platforms can use it at > some point. > > So I would ask that, instead of sweeping it under the rug, you > help work on fixing the problem you've uncovered. OK, I understand that. To be honest I tried that: changing the return type of iommu_tbl_range_alloc() to dma_addr_t and taking it from there. This resulted in quite some changes in the callers in arch/sparc, which scared me a bit because I don't have a clue about the Sparc IOMMU and I cannot test it seriously. Also I deemed it not appropriate still for the 4.3 release, which was what my patch was aiming at (because it is a 4.3 merging window regression). So I have a simpler version of the proper fix mentioned above, which simply changes the return type of iommu_tbl_range_alloc() and pushes this warning away, though this still isn't right and just papers over the issue, I think. (Sending that out in a minute in a separate mail for reference). So what is your hunch on that? Shall we go with a dual approach: Fixing the compiler warning with either the simple return type change or the Kconfig approach now for 4.3 and revert that after the actual culprit gets fixed later? Or do you know of a simpler way to fixing it properly which could make it still into 4.3? Cheers, Andre.
From: Andre Przywara <andre.przywara@arm.com> Date: Fri, 18 Sep 2015 10:03:40 +0100 > Or do you know of a simpler way to fixing it properly which could make > it still into 4.3? All I worry about is that if you take it out of the build, doing the proper fix will suddenly become very low priority and be forgotten about completely. Whereas if it actually blocks the build for someone, it's a high priority issue to address.
Hi David, On 18/09/15 18:09, David Miller wrote: > From: Andre Przywara <andre.przywara@arm.com> > Date: Fri, 18 Sep 2015 10:03:40 +0100 > >> Or do you know of a simpler way to fixing it properly which could make >> it still into 4.3? > > All I worry about is that if you take it out of the build, doing > the proper fix will suddenly become very low priority and be > forgotten about completely. > > Whereas if it actually blocks the build for someone, it's a high > priority issue to address. I see. What about if I provide the two patches at the same time? An easy fix for 4.3 and the proper fix for 4.4? You can then even choose to take the proper fix for 4.3 if it's reasonably low risk. I will try sending something on Monday. Cheers, Andre.
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig index 56442d2..1cedb7e 100644 --- a/arch/sparc/Kconfig +++ b/arch/sparc/Kconfig @@ -93,6 +93,9 @@ config IOMMU_HELPER bool default y if SPARC64 +config IOMMU_TBL_HELPER + def_bool y if IOMMU_HELPER + config STACKTRACE_SUPPORT bool default y if SPARC64 diff --git a/lib/Makefile b/lib/Makefile index 13a7c6a..82944a1 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -113,7 +113,8 @@ obj-$(CONFIG_AUDIT_GENERIC) += audit.o obj-$(CONFIG_AUDIT_COMPAT_GENERIC) += compat_audit.o obj-$(CONFIG_SWIOTLB) += swiotlb.o -obj-$(CONFIG_IOMMU_HELPER) += iommu-helper.o iommu-common.o +obj-$(CONFIG_IOMMU_HELPER) += iommu-helper.o +obj-$(CONFIG_IOMMU_TBL_HELPER) += iommu-common.o obj-$(CONFIG_FAULT_INJECTION) += fault-inject.o obj-$(CONFIG_NOTIFIER_ERROR_INJECTION) += notifier-error-inject.o obj-$(CONFIG_CPU_NOTIFIER_ERROR_INJECT) += cpu-notifier-error-inject.o
Though the file lib/iommu_common.c resides in a common directory, the code in there is actually only used by Sparc(64). The recent change of DMA_ERROR_CODE in the ARM tree now generates a compiler warning when compiled with LPAE support (where dma_addr_t is u64, but unsigned long is still u32): ********* In file included from /src/linux/include/linux/dma-mapping.h:86:0, from /src/linux/lib/iommu-common.c:11: /src/linux/lib/iommu-common.c: In function 'iommu_tbl_range_alloc': /src/linux/arch/arm/include/asm/dma-mapping.h:16:24: warning: large integer implicitly truncated to unsigned type [-Woverflow] #define DMA_ERROR_CODE (~(dma_addr_t)0x0) ^ /src/linux/lib/iommu-common.c:127:10: note: in expansion of macro 'DMA_ERROR_CODE' return DMA_ERROR_CODE; ^ ********* It seems the types used in this file are not really correct, but a fix isn't trivial. So for the time being restrict this code to be compiled only when we actually need it. Compile tested on Sparc, Sparc64, PPC64, ARM, ARM64, x86. Signed-off-by: Andre Przywara <andre.przywara@arm.com> --- arch/sparc/Kconfig | 3 +++ lib/Makefile | 3 ++- 2 files changed, 5 insertions(+), 1 deletion(-)