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xen-devel
[Xen-devel] Re: Vanilla Linux and has_foreign_mapping
Michael Abd-El-Malek wrote:
I'm trying to add support to Linux 2.6.25 for the
"has_foreign_mappings" MMU context flag. Xen's Linux 2.6.18 tree uses
this flag, so that page tables are properly disposed of when an
application exits when it has foreign mappings.
I was hoping to avoid having to introduce that flag, but I have to admit
I haven't given it much analysis. How are you using it?
See:
http://lists.xensource.com/archives/html/xen-devel/2006-08/msg00038.html
Here is my attempt:
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 2a054ef..3e51897 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -633,8 +633,13 @@ void xen_exit_mmap(struct mm_struct *mm)
spin_lock(&mm->page_table_lock);
/* pgd may not be pinned in the error exit path of execve */
- if (PagePinned(virt_to_page(mm->pgd)))
- xen_pgd_unpin(mm->pgd);
+ if (PagePinned(virt_to_page(mm->pgd))) {
+ if (mm->context.has_foreign_mappings) {
+ printk("%s: because of has_foreign_mappings, delaying
unpinning\n", __FUNCTION__);
+ } else {
+ xen_pgd_unpin(mm->pgd);
+ }
+ }
spin_unlock(&mm->page_table_lock);
}
diff --git a/include/asm-x86/mmu.h b/include/asm-x86/mmu.h
index efa962c..7194698 100644
--- a/include/asm-x86/mmu.h
+++ b/include/asm-x86/mmu.h
@@ -18,6 +18,9 @@ typedef struct {
int size;
struct mutex lock;
void *vdso;
+#ifdef CONFIG_XEN
+ int has_foreign_mappings;
+#endif
} mm_context_t;
#ifdef CONFIG_SMP
Unfortunately, I got the following kernel crash on process exit:
BUG: unable to handle kernel paging request at ebdae008
IP: [<c01157f9>] pgd_mop_up_pmds+0x6a/0xd8
Which line is that?
J
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