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[Xen-devel] one question on __user_pgd
| To: | xen-devel@xxxxxxxxxxxxxxxxxxx |
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| Subject: | [Xen-devel] one question on __user_pgd |
| From: | leilei175@xxxxxxxxx |
| Date: | Tue, 19 May 2009 22:17:58 +0800 |
| Delivery-date: | Tue, 19 May 2009 07:19:02 -0700 |
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in the mm_pin routine,
the function would do
mm_walk(mm, PAGE_KERNEL_RO);
xen_pgd_pin(__pa(mm->pgd)); /* kernel */
xen_pgd_pin(__pa(__user_pgd(mm->pgd))); /* user */
mm->context.pinned = 1;
then I saw the macro __user_pgd is defined as
#define __user_pgd(pgd) ((pgd) + PTRS_PER_PGD)
my question is:
what's the use of __user_pgd?
moreover, concerning the action of "pin" the page directory table,
what is the use of it?
could some one shed some light on these questions? Any explanation is
appreciated.
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