On Mon, May 20, 2013 at 05:19:26PM +0800, Xiao Guangrong wrote:
> On 05/19/2013 06:47 PM, Gleb Natapov wrote:
> > On Fri, May 17, 2013 at 05:12:57AM +0800, Xiao Guangrong wrote:
> >> Move deletion shadow page from the hash list from kvm_mmu_commit_zap_page to
> >> kvm_mmu_prepare_zap_page so that we can call kvm_mmu_commit_zap_page
> >> once for multiple kvm_mmu_prepare_zap_page that can help us to avoid
> >> unnecessary TLB flush
> >>
> > Don't we call kvm_mmu_commit_zap_page() once for multiple
> > kvm_mmu_prepare_zap_page() now when possible? kvm_mmu_commit_zap_page()
> > gets a list as a parameter. I am not against the change, but wish to
> > understand it better.
>
> The changelong is not clear enough, i mean we can "call
> kvm_mmu_commit_zap_page once for multiple kvm_mmu_prepare_zap_page" when
> we use lock-break technique. If we do not do this, the page can be found
> in hashtable but they are linked on the invalid_list on other thread.
>
Got it. Make sense.
> >
> >> Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
> >> ---
> >> arch/x86/kvm/mmu.c | 8 ++++++--
> >> 1 files changed, 6 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> >> index 40d7b2d..682ecb4 100644
> >> --- a/arch/x86/kvm/mmu.c
> >> +++ b/arch/x86/kvm/mmu.c
> >> @@ -1466,7 +1466,7 @@ static inline void kvm_mod_used_mmu_pages(struct kvm *kvm, int nr)
> >> static void kvm_mmu_free_page(struct kvm_mmu_page *sp)
> >> {
> >> ASSERT(is_empty_shadow_page(sp->spt));
> >> - hlist_del(&sp->hash_link);
> >> +
> >> list_del(&sp->link);
> >> free_page((unsigned long)sp->spt);
> >> if (!sp->role.direct)
> >> @@ -1655,7 +1655,8 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm,
> >>
> >> #define for_each_gfn_indirect_valid_sp(_kvm, _sp, _gfn) \
> >> for_each_gfn_sp(_kvm, _sp, _gfn) \
> >> - if ((_sp)->role.direct || (_sp)->role.invalid) {} else
> >> + if ((_sp)->role.direct || \
> >> + ((_sp)->role.invalid && WARN_ON(1))) {} else
> >>
> >> /* @sp->gfn should be write-protected at the call site */
> >> static int __kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
> >> @@ -2074,6 +2075,9 @@ static int kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp,
> >> unaccount_shadowed(kvm, sp->gfn);
> >> if (sp->unsync)
> >> kvm_unlink_unsync_page(kvm, sp);
> >> +
> >> + hlist_del_init(&sp->hash_link);
> >> +
> > What about moving this inside if() bellow and making it hlist_del()?
> > Leave the page on the hash if root_count is non zero.
> >
>
> It's a good idea. will update.
>
--
Gleb.
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