From: Rik van Riel <riel@redhat.com>
To: Simon Jeons <simon.jeons@gmail.com>
Cc: Linux Memory Management List <linux-mm@kvack.org>,
Dave Hansen <dave.hansen@intel.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@suse.cz>, Mel Gorman <mgorman@suse.de>
Subject: Re: vmalloc fault
Date: Fri, 26 Apr 2013 06:04:40 -0400 [thread overview]
Message-ID: <517A5138.9040902@redhat.com> (raw)
In-Reply-To: <517A4F1E.9070803@gmail.com>
On 04/26/2013 05:55 AM, Simon Jeons wrote:
> Hi all,
>
> 1. Why vmalloc fault need sync user process page table with kernel page
> table instead of using kernel page table directly?
Each process has its own PGD, into which both kernel and user
PMDs (or PUDs) are mapped. It is possible the PGD is missing
some pointers, that need to be filled in at fault time.
> 2. Why do_swap_page doesn't set present flag?
It does. Look at how vm_get_page_prot works.
> 3. When enable DEBUG_PAGEALLOC(catch use-after-free bug), if user
> process alloc pages from zone_normal(which is direct mapping) when
> fallback, this page which allocated for user process will set present
> flag in related pte, correct? but why also set present flag for kernel
> direct mapping? Does kernel have any requirement to access it?
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next prev parent reply other threads:[~2013-04-26 10:04 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-26 9:55 vmalloc fault Simon Jeons
2013-04-26 10:04 ` Rik van Riel [this message]
2013-04-26 10:17 ` Simon Jeons
2013-04-26 10:19 ` Rik van Riel
2013-04-26 10:27 ` Simon Jeons
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