Jeremy Fitzhardinge wrote:
Currently, the set_lazy_mode pv_op is overloaded with 5 functions:
1. enter lazy cpu mode
2. leave lazy cpu mode
3. enter lazy mmu mode
4. leave lazy mmu mode
5. flush pending batched operations
This complicates each paravirt backend, since it needs to deal with
all the possible state transitions, handling flushing, etc. In
particular, flushing is quite distinct from the other 4 functions, and
seems to just cause complication.
This patch removes the set_lazy_mode operation, and adds "enter" and
"leave" lazy mode operations on mmu_ops and cpu_ops. All the logic
associated with enter and leaving lazy states is now in common code
(basically BUG_ONs to make sure that no mode is current when entering
a lazy mode, and make sure that the mode is current when leaving).
Also, flush is handled in a common way, by simply leaving and
re-entering the lazy mode.
The result is that the Xen and VMI lazy mode implementations are much
simpler; as would lguest's be.
The code doesn't support having both lazy modes active at once. Maybe
that's not an issue, but aren't the two modes orthogonal?
--- a/arch/i386/xen/multicalls.h
+++ b/arch/i386/xen/multicalls.h
@@ -35,7 +35,7 @@ void xen_mc_flush(void);
/* Issue a multicall if we're not in a lazy mode */
static inline void xen_mc_issue(unsigned mode)
{
- if ((xen_get_lazy_mode() & mode) == 0)
+ if ((paravirt_get_lazy_mode() & mode) == 0)
xen_mc_flush();
This snippet looks like it wants to support concurrently active lazy modes.
--
Any sufficiently difficult bug is indistinguishable from a feature.
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