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Date: Wed, 23 May 2012 11:40:46 -0700 From: Yinghai Lu <yinghai@...nel.org> To: Linus Torvalds <torvalds@...ux-foundation.org>, Steven Newbury <steve@...wbury.org.uk>, "H. Peter Anvin" <hpa@...or.com> Cc: Bjorn Helgaas <bhelgaas@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 02/11] PCI: Try to allocate mem64 above 4G at first On Wed, May 23, 2012 at 10:30 AM, Yinghai Lu <yinghai@...nel.org> wrote: > On Wed, May 23, 2012 at 8:57 AM, Linus Torvalds > <torvalds@...ux-foundation.org> wrote: >> On Tue, May 22, 2012 at 11:34 PM, Yinghai Lu <yinghai@...nel.org> wrote: >>> and will fall back to below 4g if it can not find any above 4g. >> >> Has this been tested on 32-bit machines without PAE? There might be >> things that just happen to work because their allocations were always >> done bottom-up. > > Good point. that problem should be addressed at first before this patch. Just checked code for 32bit machines without PAE. when X86_PAE is not set, phys_addr_t aka resource_size_t will be 32bit. so in drivers/pci/bus.c::pci_bus_alloc_resource_fit() will have bottom to 0. resource_size_t bottom = PCIBIOS_MAX_MEM_32 + 1ULL; also in arch/x86/kernel/setup.c::setup_arch() iomem_resource.end = (1ULL << boot_cpu_data.x86_phys_bits) - 1; will have iomem_resource.end to 0xffffffff when X86_PAE is set, but CPU does not support PAE. phys_addr_t aka resource_size_t will be 32bit. so in drivers/pci/bus.c::pci_bus_alloc_resource_fit() will have bottom to 4g. resource_size_t bottom = PCIBIOS_MAX_MEM_32 + 1ULL; but in arch/x86/kernel/setup.c::setup_arch() iomem_resource.end = (1ULL << boot_cpu_data.x86_phys_bits) - 1; will have iomem_resource.end to 0xffffffff, because x86_phys_bits is 32 when PAE is not detected in arch/x86/kernel/cpu/common.c::get_cpu_cap. that mean first try will fail, so it will go to second try with bottom to 0. so both case are safe with this patch. Thanks Yinghai -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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