diff options
Diffstat (limited to 'drivers/lguest/lguest_asm.S')
| -rw-r--r-- | drivers/lguest/lguest_asm.S | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/drivers/lguest/lguest_asm.S b/drivers/lguest/lguest_asm.S index 3126ae923cc..f182c6a3620 100644 --- a/drivers/lguest/lguest_asm.S +++ b/drivers/lguest/lguest_asm.S @@ -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*! * |