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lguest: documentation VII: FIXMEs

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Documentation: The FIXMEs

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Rusty Russell
2007-07-26 10:41:05 -07:00
committed by Linus Torvalds
parent f8f0fdcd40
commit f56a384e98
9 changed files with 89 additions and 0 deletions
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14
drivers/lguest/interrupts_and_traps.c
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@ -231,6 +231,20 @@ static int direct_trap(const struct lguest *lg,
* go direct, of course 8) */
return idt_type(trap->a, trap->b) == 0xF;
}
/*:*/
/*M:005 The Guest has the ability to turn its interrupt gates into trap gates,
* if it is careful. The Host will let trap gates can go directly to the
* Guest, but the Guest needs the interrupts atomically disabled for an
* interrupt gate. It can do this by pointing the trap gate at instructions
* within noirq_start and noirq_end, where it can safely disable interrupts. */
/*M:006 The Guests do not use the sysenter (fast system call) instruction,
* because it's hardcoded to enter privilege level 0 and so can't go direct.
* It's about twice as fast as the older "int 0x80" system call, so it might
* still be worthwhile to handle it in the Switcher and lcall down to the
* Guest. The sysenter semantics are hairy tho: search for that keyword in
* entry.S :*/
/*H:260 When we make traps go directly into the Guest, we need to make sure
* the kernel stack is valid (ie. mapped in the page tables). Otherwise, the