korg/linux
0
0
Fork 0
mirror of https://mirrors.bfsu.edu.cn/git/linux.git synced 2024-11-17 09:14:19 +08:00
Code Issues Packages Projects Releases Wiki Activity

[PATCH] i386: iOPL handling for paravirt guests

Browse Source 
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@vmware.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
This commit is contained in:
Zachary Amsden 2007-02-13 13:26:21 +01:00 committed by Andi Kleen
parent 9226d125d9
commit 8b15114434
1 changed files with 9 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
arch/i386/kernel/process.c
View File

@ -669,6 +669,15 @@ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct tas
*/
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
*/