From: Simon Jeons <simon.jeons@gmail.com>
To: Tang Chen <tangchen@cn.fujitsu.com>
Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org,
linux-mm@kvack.org, paulus@samba.org, hpa@zytor.com,
sparclinux@vger.kernel.org, cl@linux.com,
linux-s390@vger.kernel.org, x86@kernel.org,
linux-acpi@vger.kernel.org, isimatu.yasuaki@jp.fujitsu.com,
linfeng@cn.fujitsu.com, mgorman@suse.de,
kosaki.motohiro@jp.fujitsu.com, rientjes@google.com,
len.brown@intel.com, wency@cn.fujitsu.com, cmetcalf@tilera.com,
glommer@parallels.com, Jianguo Wu <wujianguo@huawei.com>,
yinghai@kernel.org, laijs@cn.fujitsu.com,
linux-kernel@vger.kernel.org, minchan.kim@gmail.com,
akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v6 00/15] memory-hotplug: hot-remove physical memory
Date: Thu, 31 Jan 2013 21:06:25 -0600 [thread overview]
Message-ID: <1359687985.1303.15.camel@kernel> (raw)
In-Reply-To: <510B2B8A.7040407@cn.fujitsu.com>
Hi Tang,
On Fri, 2013-02-01 at 10:42 +0800, Tang Chen wrote:
I confuse!
> Hi Simon,
>
> On 02/01/2013 10:17 AM, Simon Jeons wrote:
> >> For example:
> >>
> >> 64TB, what ever
> >> xxxTB, what ever
> >> logic address space: |_____kernel_______|_________user_________________|
> >> \ \ / /
> >> \ /\ /
> >> physical address space: |___\/__\/_____________| 4GB or
> >> 8GB, what ever
> >> *****
> >
> > How much address space user process can have on x86_64? Also 8GB?
>
> Usually, we don't say that.
>
> 8GB is your physical memory, right ?
> But kernel space and user space is the logic conception in OS. They are
> in logic
> address space.
>
> So both the kernel space and the user space can use all the physical memory.
> But if the page is already in use by either of them, the other one
> cannot use it.
> For example, some pages are direct mapped to kernel, and is in use by
> kernel, the
> user space cannot map it.
How can distinguish map and use? I mean how can confirm memory is used
by kernel instead of map?
>
> >
> >>
> >> The ***** part physical is mapped to user space in the process' own
> >> pagetable.
> >> It is also direct mapped in kernel's pagetable. So the kernel can also
> >> access it. :)
> >
> > But how to protect user process not modify kernel memory?
>
> This is the job of CPU. On intel cpus, user space code is running in
> level 3, and
> kernel space code is running in level 0. So the code in level 3 cannot
> access the data
> segment in level 0.
1) If user process and kenel map to same physical memory, user process
will get SIGSEGV during #PF if access to this memory, but If user proces
s will map to the same memory which kernel map? Why? It can't access it.
2) If two user processes map to same physical memory, what will happen
if one process access the memory?
>
> Thanks. :)
next prev parent reply other threads:[~2013-02-01 3:06 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-09 9:32 [PATCH v6 00/15] memory-hotplug: hot-remove physical memory Tang Chen
2013-01-09 9:32 ` [PATCH v6 01/15] memory-hotplug: try to offline the memory twice to avoid dependence Tang Chen
2013-01-09 9:32 ` [PATCH v6 02/15] memory-hotplug: check whether all memory blocks are offlined or not when removing memory Tang Chen
2013-01-09 23:11 ` Andrew Morton
2013-01-10 5:56 ` Tang Chen
2013-01-09 9:32 ` [PATCH v6 03/15] memory-hotplug: remove redundant codes Tang Chen
2013-01-09 9:32 ` [PATCH v6 04/15] memory-hotplug: remove /sys/firmware/memmap/X sysfs Tang Chen
2013-01-09 22:49 ` Andrew Morton
2013-01-10 6:07 ` Tang Chen
2013-01-09 23:19 ` Andrew Morton
2013-01-10 6:15 ` Tang Chen
2013-01-09 9:32 ` [PATCH v6 05/15] memory-hotplug: introduce new function arch_remove_memory() for removing page table depends on architecture Tang Chen
2013-01-09 22:50 ` Andrew Morton
2013-01-10 2:25 ` Tang Chen
2013-01-09 9:32 ` [PATCH v6 06/15] memory-hotplug: implement register_page_bootmem_info_section of sparse-vmemmap Tang Chen
2013-01-09 9:32 ` [PATCH v6 07/15] memory-hotplug: move pgdat_resize_lock into sparse_remove_one_section() Tang Chen
2013-01-09 9:32 ` [PATCH v6 08/15] memory-hotplug: Common APIs to support page tables hot-remove Tang Chen
2013-01-29 13:02 ` Simon Jeons
2013-01-30 1:53 ` Jianguo Wu
2013-01-30 2:13 ` Simon Jeons
2013-01-29 13:04 ` Simon Jeons
2013-01-30 2:16 ` Tang Chen
2013-01-30 3:27 ` Simon Jeons
2013-01-30 5:55 ` Tang Chen
2013-01-30 7:32 ` Simon Jeons
2013-02-04 23:04 ` Andrew Morton
2013-01-09 9:32 ` [PATCH v6 09/15] memory-hotplug: remove page table of x86_64 architecture Tang Chen
2013-01-09 9:32 ` [PATCH v6 10/15] memory-hotplug: remove memmap of sparse-vmemmap Tang Chen
2013-01-09 9:32 ` [PATCH v6 11/15] memory-hotplug: Integrated __remove_section() of CONFIG_SPARSEMEM_VMEMMAP Tang Chen
2013-01-09 9:32 ` [PATCH v6 12/15] memory-hotplug: memory_hotplug: clear zone when removing the memory Tang Chen
2013-01-09 9:32 ` [PATCH v6 13/15] memory-hotplug: remove sysfs file of node Tang Chen
2013-01-09 9:32 ` [PATCH v6 14/15] memory-hotplug: free node_data when a node is offlined Tang Chen
2013-01-09 9:32 ` [PATCH v6 15/15] memory-hotplug: Do not allocate pdgat if it was not freed when offline Tang Chen
2013-01-09 22:23 ` [PATCH v6 00/15] memory-hotplug: hot-remove physical memory Andrew Morton
2013-01-10 2:17 ` Tang Chen
2013-01-10 7:14 ` Glauber Costa
2013-01-10 7:31 ` Kamezawa Hiroyuki
2013-01-10 7:55 ` Glauber Costa
2013-01-10 8:23 ` Kamezawa Hiroyuki
2013-01-10 8:36 ` Glauber Costa
2013-01-10 8:39 ` Kamezawa Hiroyuki
2013-01-09 23:33 ` Andrew Morton
2013-01-10 2:18 ` Tang Chen
2013-01-29 12:52 ` Simon Jeons
2013-01-30 2:32 ` Tang Chen
2013-01-30 2:48 ` Simon Jeons
2013-01-30 3:00 ` Tang Chen
2013-01-30 10:15 ` Tang Chen
2013-01-30 10:18 ` Tang Chen
2013-01-31 1:22 ` Simon Jeons
2013-01-31 3:31 ` Tang Chen
2013-01-31 6:19 ` Simon Jeons
2013-01-31 7:10 ` Tang Chen
2013-01-31 8:17 ` Simon Jeons
2013-01-31 8:48 ` Simon Jeons
2013-01-31 9:44 ` Tang Chen
2013-01-31 10:38 ` Simon Jeons
2013-02-01 1:32 ` Jianguo Wu
2013-02-01 1:36 ` Simon Jeons
2013-02-01 1:57 ` Jianguo Wu
2013-02-01 2:06 ` Simon Jeons
2013-02-01 2:18 ` Jianguo Wu
2013-02-01 1:57 ` Tang Chen
2013-02-01 2:17 ` Simon Jeons
2013-02-01 2:42 ` Tang Chen
2013-02-01 3:06 ` Simon Jeons [this message]
2013-02-01 3:39 ` Tang Chen
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