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Date: Sat, 10 Feb 2007 12:52:31 +0100 (CET) From: Andi Kleen <ak@...e.de> To: Zachary Amsden <zach@...are.com>, Andi Kleen <ak@...e.de>, Jeremy Fitzhardinge <jeremy@...source.com>, Rusty Russell <rusty@...tcorp.com.au>, Chris Wright <chrisw@...s-sol.org>, patches@...-64.org, linux-kernel@...r.kernel.org Subject: [PATCH 2.6.21 review II] [3/10] i386: iOPL handling for paravirt guests From: Zachary Amsden <zach@...are.com> 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. Signed-off-by: Zachary Amsden <zach@...are.com> Signed-off-by: Andi Kleen <ak@...e.de> Cc: Andi Kleen <ak@...e.de> Cc: Jeremy Fitzhardinge <jeremy@...source.com> Cc: Rusty Russell <rusty@...tcorp.com.au> Cc: Chris Wright <chrisw@...s-sol.org> Signed-off-by: Andrew Morton <akpm@...l.org> --- arch/i386/kernel/process.c | 9 +++++++++ 1 file changed, 9 insertions(+) Index: linux/arch/i386/kernel/process.c =================================================================== --- linux.orig/arch/i386/kernel/process.c +++ linux/arch/i386/kernel/process.c @@ -670,6 +670,15 @@ 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@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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