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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/lguest_asm.S
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@@ -39,6 +39,20 @@ LGUEST_PATCH(pushf, movl lguest_data+LGUEST_DATA_irq_enabled, %eax)
.global lguest_noirq_start
.global lguest_noirq_end
/*M:004 When the Host reflects a trap or injects an interrupt into the Guest,
* it sets the eflags interrupt bit on the stack based on
* lguest_data.irq_enabled, so the Guest iret logic does the right thing when
* restoring it. However, when the Host sets the Guest up for direct traps,
* such as system calls, the processor is the one to push eflags onto the
* stack, and the interrupt bit will be 1 (in reality, interrupts are always
* enabled in the Guest).
*
* This turns out to be harmless: the only trap which should happen under Linux
* with interrupts disabled is Page Fault (due to our lazy mapping of vmalloc
* regions), which has to be reflected through the Host anyway. If another
* trap *does* go off when interrupts are disabled, the Guest will panic, and
* we'll never get to this iret! :*/
/*G:045 There is one final paravirt_op that the Guest implements, and glancing
* at it you can see why I left it to last. It's *cool*! It's in *assembler*!
*