From: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
To: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH 2/4] KVM: MMU: support unsync sp out of the protection of 'mmu_lock'
Date: Thu, 23 Sep 2010 11:05:15 +0800 [thread overview]
Message-ID: <4C9AC3EB.1080507@cn.fujitsu.com> (raw)
In-Reply-To: <4C977B9E.6030208@redhat.com>
On 09/20/2010 11:19 PM, Avi Kivity wrote:
> On 09/20/2010 04:19 PM, Xiao Guangrong wrote:
>> It allows keep unsync sp alive while it's out of the protection, later
>> we can use
>> kvm_mmu_free_page() to free it if !sp->active_count
>
> Don't understand. Of course unsync pages exist outside mmu_lock...?
Yes.
sorry, not describe it clear in the log.
>
>
>> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
>> index 839852d..4b7af3f 100644
>> --- a/arch/x86/kvm/mmu.c
>> +++ b/arch/x86/kvm/mmu.c
>> @@ -996,7 +996,6 @@ static void kvm_mmu_free_page(struct kvm *kvm,
>> struct kvm_mmu_page *sp)
>> {
>> ASSERT(is_empty_shadow_page(sp->spt));
>> hlist_del(&sp->hash_link);
>> - list_del(&sp->link);
>> __free_page(virt_to_page(sp->spt));
>> if (!sp->role.direct)
>> __free_page(virt_to_page(sp->gfns));
>> @@ -1681,9 +1680,8 @@ static int kvm_mmu_prepare_zap_page(struct kvm
>> *kvm, struct kvm_mmu_page *sp,
>> kvm_mmu_unlink_parents(kvm, sp);
>> if (!sp->role.invalid&& !sp->role.direct)
>> unaccount_shadowed(kvm, sp->gfn);
>> - if (sp->unsync)
>> - kvm_unlink_unsync_page(kvm, sp);
>> - if (!sp->active_count) {
>> +
>> + if (!sp->active_count || sp->unsync) {
>> /* Count self */
>> ret++;
>> list_move(&sp->link, invalid_list);
>
> How can you drop an active unsync page?
>
> I'm missing something here.
>
Umm, this feature is used like this:
hold mmu_lock
increase sp->active_count
release mmu_lock
......
hold mmu_lock
increase sp->active_count
if (!sp->active_count && sp->invalid)
kvm_mmu_free_page(sp);
......
release mmu_lock
next prev parent reply other threads:[~2010-09-23 3:00 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-20 14:18 [PATCH 1/4] KVM: MMU: rename 'sp->root_count' to 'sp->active_count' Xiao Guangrong
2010-09-20 14:19 ` [PATCH 2/4] KVM: MMU: support unsync sp out of the protection of 'mmu_lock' Xiao Guangrong
2010-09-20 15:19 ` Avi Kivity
2010-09-23 3:05 ` Xiao Guangrong [this message]
2010-09-26 13:02 ` Avi Kivity
2010-09-20 14:20 ` [PATCH 3/4] KVM: MMU: move reserved bits check to FNAME(update_pte) Xiao Guangrong
2010-09-20 14:21 ` [PATCH 4/4] KVM: MMU: Don't touch unsync sp in kvm_mmu_pte_write() Xiao Guangrong
2010-09-20 15:24 ` Avi Kivity
2010-09-23 2:59 ` Xiao Guangrong
2010-09-26 13:09 ` Avi Kivity
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