Messages in this thread | | | From | Bjorn Helgaas <> | Date | Tue, 12 Jun 2012 04:30:33 -0700 | Subject | Re: [PATCH 1/2 v2] x86: add max_addr boot option |
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On Mon, Jun 11, 2012 at 11:29 PM, Wen Congyang <wency@cn.fujitsu.com> wrote: > At 06/12/2012 01:35 AM, Bjorn Helgaas Wrote: >> On Mon, Jun 11, 2012 at 1:44 AM, Wen Congyang <wency@cn.fujitsu.com> wrote: >>> Currently, the boot option max_addr is only supported on ia64 platform. >>> We also need it on x86 platform. >>> For example: >>> There are two nodes: >>> NODE#0 address range 0x00000000 00000000 - 0x00010000 00000000 >>> NODE#1 address range 0x00010000 00000000 - 0x00020000 00000000 >>> If we only want to use node0, we can specify the max_addr. The boot >>> option "mem=" can do the same thing now. But the boot option "mem=" >>> means the total memory used by the system. If we tell the user >>> that the boot option "mem=" can do this, it will confuse the user. >>> So we need an new boot option "max_addr" on x86 platform. >> >> I don't object to this patch (and thanks for tweaking the mem range printk). >> >> I don't know what your use case is, but from a user interface >> perspective, the "max_addr=" option feels like a bit of a hack. If >> you're trying to avoid use of other nodes, "max_addr" is an awkward >> way to do it. It requires the user to know the physical address -> >> node mappings, and it doesn't affect the CPUs and I/O resources on >> other nodes. You could implement a "numa_node=" or similar parameter >> that would allow you to ignore remote memory, CPUs, and I/O. > > Currently, I only need to ignore the memory. If we need to ignore a node, > "numa_node=" or similar parameter is a better choice.
Doesn't the end user have to know the memory map of the system to use "max_addr="? How do you know what value to supply? Do you have to attempt a boot once to discover the highest address on node 0? What if node 0 and node 1 memory are interleaved, so there's some node 1 memory below the highest node 0 address?
>>> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com> >>> --- >>> Documentation/kernel-parameters.txt | 2 +- >>> arch/x86/kernel/e820.c | 36 +++++++++++++++++++++++++++++++++++ >>> 2 files changed, 37 insertions(+), 1 deletions(-) >>> >>> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt >>> index a92c5eb..034609d 100644 >>> --- a/Documentation/kernel-parameters.txt >>> +++ b/Documentation/kernel-parameters.txt >>> @@ -1441,7 +1441,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted. >>> yeeloong laptop. >>> Example: machtype=lemote-yeeloong-2f-7inch >>> >>> - max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater >>> + max_addr=nn[KMG] [KNL,BOOT,ia64,X86] All physical memory greater >>> than or equal to this physical address is ignored. >>> >>> maxcpus= [SMP] Maximum number of processors that an SMP kernel >>> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c >>> index 4185797..cd07226 100644 >>> --- a/arch/x86/kernel/e820.c >>> +++ b/arch/x86/kernel/e820.c >>> @@ -47,6 +47,7 @@ unsigned long pci_mem_start = 0xaeedbabe; >>> #ifdef CONFIG_PCI >>> EXPORT_SYMBOL(pci_mem_start); >>> #endif >>> +static u64 max_addr = ~0ULL; >>> >>> /* >>> * This function checks if any part of the range <start,end> is mapped >>> @@ -119,6 +120,20 @@ static void __init __e820_add_region(struct e820map *e820x, u64 start, u64 size, >>> return; >>> } >>> >>> + if (start >= max_addr) { >>> + printk(KERN_ERR "e820: ignoring [mem %#010llx-%#010llx]\n", >>> + (unsigned long long)start, >>> + (unsigned long long)(start + size - 1)); >>> + return; >>> + } >>> + >>> + if (max_addr - start < size) { >>> + printk(KERN_ERR "e820: ignoring [mem %#010llx-%#010llx]\n", >>> + (unsigned long long)max_addr, >>> + (unsigned long long)(start + size - 1)); >>> + size = max_addr - start; >>> + } >>> + >>> e820x->map[x].addr = start; >>> e820x->map[x].size = size; >>> e820x->map[x].type = type; >>> @@ -835,6 +850,22 @@ static int __init parse_memopt(char *p) >>> } >>> early_param("mem", parse_memopt); >>> >>> +static int __init parse_memmax_opt(char *p) >>> +{ >>> + char *oldp; >>> + >>> + if (!p) >>> + return -EINVAL; >>> + >>> + oldp = p; >>> + max_addr = memparse(p, &p); >>> + if (p == oldp) >>> + return -EINVAL; >>> + >>> + return 0; >>> +} >>> +early_param("max_addr", parse_memmax_opt); >>> + >>> static int __init parse_memmap_opt(char *p) >>> { >>> char *oldp; >>> @@ -881,6 +912,11 @@ early_param("memmap", parse_memmap_opt); >>> >>> void __init finish_e820_parsing(void) >>> { >>> + if (max_addr != ~0ULL) { >>> + userdef = 1; >>> + e820_remove_range(max_addr, ULLONG_MAX - max_addr, E820_RAM, 1); >>> + } >>> + >>> if (userdef) { >>> u32 nr = e820.nr_map; >>> >>> -- >>> 1.7.1 >>> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ >> > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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