On Mon, Jan 06, 2014 at 08:28:20PM +0100, Krzysztof Hałasa wrote: > Russell, Santosh, > > the unneeded commit causing regression is still in place. Please try to > compile an ARM kernel without CONFIG_ARM_PATCH_PHYS_VIRT and with > CONFIG_ZONE_DMA and see for yourself, if you don't believe me. > > Please be aware that this commit fixes nothing, its only function is > causing the regression - so we don't lose anything by reverting it. > > If the attached wasn't clear, what the defective commit presently does > is changing a perfectly valid code into a code referencing a variable > which (without CONFIG_ARM_PATCH_PHYS_VIRT set) doesn't at all exist. > > With CONFIG_ARM_PATCH_PHYS_VIRT set, this commit does precisely nothing.
Right, so, with Assabet, which has CONFIG_DMA_ZONE=y and CONFIG_ARM_PATCH_PHYS_VIRT=y: $ make O=../build/assabet arch/arm/mm/init.i gives: arm_dma_limit = __pv_phys_offset + arm_dma_zone_size - 1; with or without Santosh's patch. So, with V2P patching in place, there's absolutely no functional difference. With CONFIG_ARM_PATCH_PHYS_VIRT=n, before Santosh's patch: arm_dma_limit = (0xc0000000UL) + arm_dma_zone_size - 1; After: arm_dma_limit = __pv_phys_offset + arm_dma_zone_size - 1; and this breaks the build because there is no __pv_phys_offset symbol. Now, the case which matters for Santosh is the first case - the one where CONFIG_ARM_PATCH_PHYS_VIRT=y. We can clearly see that after preprocessing, the results are 100% identical. Therefore, I find myself agreeing with Krzysztof that the commit is bad, has no functional change for the case it was proposed to solve, and needs to be reverted. -- FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up. Estimation in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad. Estimate before purchase was "up to 13.2Mbit". -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
