On Wed, 13 Mar 2013 13:06:23 +0800
Xiao Guangrong <xiaoguangr...@linux.vnet.ibm.com> wrote:
> On 03/12/2013 04:44 PM, Takuya Yoshikawa wrote:
> > This will be used not to zap unrelated mmu pages when creating/moving
> > a memory slot later.
>
> How about save all mmio spte into a mmio-rmap?
The problem is that other mmu code would need to care about the pointers
stored in the new rmap list: when mmu_shrink zaps shadow pages for example.
Maybe worth thinking about, but I want to have a simple, back-portable patch
for distributors, as a first step: note that creating a memory slot can happen
many times for some guest configurations since QEMU is doing strange things
for re-mapping some regions IIRC.
>
> The good things are:
> - instead walking all shadow page, we can only walk the rmap
Traversing the active list does not take such a long time compared to
other things to do for zapping pages: us, not ms order. But I'm now
preparing for an additional work to avoid "goto restart" after deleting
entries. That will at least help us not to traverse more than once.
> - Comparing to zap a shadow page, it does not need to flush TLB after
> zapping mmio sptes
If we check each spte in the sp, we can achieve the similar goal:
similar to the old remove_write_access() code. I implemented such
code but have not seen a clear improvement yet. Pros and cons will
be there.
Thanks,
Takuya
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