Messages in this thread Patch in this message | | | Date | Thu, 14 Dec 2006 22:52:09 -0800 | Subject | [PATCH 3/6] IOPL handling for paravirt guests | From | Zachary Amsden <> |
| |
I found a clever way to make the extra IOPL switching invisible to non-paravirt compiles - since kernel_rpl is statically defined to be zero there, and only non-zero rpl kernel have a problem restoring IOPL, as popf does not restore IOPL flags unless run at CPL-0.
Subject: IOPL handling for paravirt guests Signed-off-by: Zachary Amsden <zach@vmware.com>
diff -r 8110943fd7ad arch/i386/kernel/process.c --- a/arch/i386/kernel/process.c Thu Dec 14 16:15:20 2006 -0800 +++ b/arch/i386/kernel/process.c Thu Dec 14 16:21:57 2006 -0800 @@ -665,6 +665,15 @@ struct task_struct fastcall * __switch_t load_TLS(next, cpu); /* + * Restore IOPL if needed. In normal use, the flags restore + * in the switch assembly will handle this. But if the kernel + * is running virtualized at a non-zero CPL, the popf will + * not restore flags, so it must be done in a separate step. + */ + if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl)) + set_iopl_mask(next->iopl); + + /* * Now maybe handle debug registers and/or IO bitmaps */ if (unlikely((task_thread_info(next_p)->flags & _TIF_WORK_CTXSW) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |