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.
>
>> 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.
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