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Message-ID: <566FC85C.9050502@linux.intel.com>
Date: Tue, 15 Dec 2015 15:59:24 +0800
From: Kai Huang <kai.huang@...ux.intel.com>
To: Xiao Guangrong <guangrong.xiao@...ux.intel.com>,
pbonzini@...hat.com
Cc: gleb@...nel.org, mtosatti@...hat.com, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/11] KVM: MMU: use page track for non-leaf shadow pages
On 12/15/2015 03:52 PM, Kai Huang wrote:
>
>
> On 12/01/2015 02:26 AM, Xiao Guangrong wrote:
>> non-leaf shadow pages are always write protected, it can be the user
>> of page track
>>
>> Signed-off-by: Xiao Guangrong <guangrong.xiao@...ux.intel.com>
>> ---
>> arch/x86/include/asm/kvm_page_track.h | 8 +++++
>> arch/x86/kvm/mmu.c | 26 +++++++++++++---
>> arch/x86/kvm/page_track.c | 58
>> +++++++++++++++++++++++------------
>> 3 files changed, 67 insertions(+), 25 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/kvm_page_track.h
>> b/arch/x86/include/asm/kvm_page_track.h
>> index 6744234..3447dac 100644
>> --- a/arch/x86/include/asm/kvm_page_track.h
>> +++ b/arch/x86/include/asm/kvm_page_track.h
>> @@ -41,8 +41,16 @@ int kvm_page_track_create_memslot(struct
>> kvm_memory_slot *slot,
>> void kvm_page_track_free_memslot(struct kvm_memory_slot *free,
>> struct kvm_memory_slot *dont);
>> +void
>> +kvm_slot_page_track_add_page_nolock(struct kvm *kvm,
>> + struct kvm_memory_slot *slot, gfn_t gfn,
>> + enum kvm_page_track_mode mode);
>> void kvm_page_track_add_page(struct kvm *kvm, gfn_t gfn,
>> enum kvm_page_track_mode mode);
>> +void kvm_slot_page_track_remove_page_nolock(struct kvm *kvm,
>> + struct kvm_memory_slot *slot,
>> + gfn_t gfn,
>> + enum kvm_page_track_mode mode);
>> void kvm_page_track_remove_page(struct kvm *kvm, gfn_t gfn,
>> enum kvm_page_track_mode mode);
>> bool kvm_page_track_check_mode(struct kvm_vcpu *vcpu, gfn_t gfn,
>> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
>> index b23f9fc..5a2ca73 100644
>> --- a/arch/x86/kvm/mmu.c
>> +++ b/arch/x86/kvm/mmu.c
>> @@ -806,11 +806,17 @@ static void account_shadowed(struct kvm *kvm,
>> struct kvm_mmu_page *sp)
>> struct kvm_memory_slot *slot;
>> gfn_t gfn;
>> + kvm->arch.indirect_shadow_pages++;
>> gfn = sp->gfn;
>> slots = kvm_memslots_for_spte_role(kvm, sp->role);
>> slot = __gfn_to_memslot(slots, gfn);
>> +
>> + /* the non-leaf shadow pages are keeping readonly. */
>> + if (sp->role.level > PT_PAGE_TABLE_LEVEL)
>> + return kvm_slot_page_track_add_page_nolock(kvm, slot, gfn,
>> + KVM_PAGE_TRACK_WRITE);
>> +
>> kvm_mmu_gfn_disallow_lpage(slot, gfn);
>> - kvm->arch.indirect_shadow_pages++;
>> }
>> static void unaccount_shadowed(struct kvm *kvm, struct
>> kvm_mmu_page *sp)
>> @@ -819,11 +825,15 @@ static void unaccount_shadowed(struct kvm *kvm,
>> struct kvm_mmu_page *sp)
>> struct kvm_memory_slot *slot;
>> gfn_t gfn;
>> + kvm->arch.indirect_shadow_pages--;
>> gfn = sp->gfn;
>> slots = kvm_memslots_for_spte_role(kvm, sp->role);
>> slot = __gfn_to_memslot(slots, gfn);
>> + if (sp->role.level > PT_PAGE_TABLE_LEVEL)
>> + return kvm_slot_page_track_remove_page_nolock(kvm, slot, gfn,
>> + KVM_PAGE_TRACK_WRITE);
>> +
>> kvm_mmu_gfn_allow_lpage(slot, gfn);
>> - kvm->arch.indirect_shadow_pages--;
>> }
>> static bool __mmu_gfn_lpage_is_disallowed(gfn_t gfn, int level,
>> @@ -2140,12 +2150,18 @@ static struct kvm_mmu_page
>> *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
>> hlist_add_head(&sp->hash_link,
>> &vcpu->kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)]);
>> if (!direct) {
>> - if (rmap_write_protect(vcpu, gfn))
>> + /*
>> + * we should do write protection before syncing pages
>> + * otherwise the content of the synced shadow page may
>> + * be inconsistent with guest page table.
>> + */
>> + account_shadowed(vcpu->kvm, sp);
>> +
>> + if (level == PT_PAGE_TABLE_LEVEL &&
>> + rmap_write_protect(vcpu, gfn))
>> kvm_flush_remote_tlbs(vcpu->kvm);
> I think your modification is good but I am little bit confused here.
> In account_shadowed, if sp->role.level > PT_PAGE_TABLE_LEVEL, the
> sp->gfn is write protected, and this is reasonable. So why write
> protecting the gfn of PT_PAGE_TABLE_LEVEL here?
>
>> if (level > PT_PAGE_TABLE_LEVEL && need_sync)
>> kvm_sync_pages(vcpu, gfn);
>> -
>> - account_shadowed(vcpu->kvm, sp);
>> }
>> sp->mmu_valid_gen = vcpu->kvm->arch.mmu_valid_gen;
>> init_shadow_page_table(sp);
>> diff --git a/arch/x86/kvm/page_track.c b/arch/x86/kvm/page_track.c
>> index 84420df..87554d3 100644
>> --- a/arch/x86/kvm/page_track.c
>> +++ b/arch/x86/kvm/page_track.c
>> @@ -77,6 +77,26 @@ static void update_gfn_track(struct
>> kvm_memory_slot *slot, gfn_t gfn,
>> WARN_ON(val < 0);
>> }
>> +void
>> +kvm_slot_page_track_add_page_nolock(struct kvm *kvm,
>> + struct kvm_memory_slot *slot, gfn_t gfn,
>> + enum kvm_page_track_mode mode)
>> +{
>> + WARN_ON(!check_mode(mode));
>> +
>> + update_gfn_track(slot, gfn, mode, 1);
>> +
>> + /*
>> + * new track stops large page mapping for the
>> + * tracked page.
>> + */
>> + kvm_mmu_gfn_disallow_lpage(slot, gfn);
>> +
>> + if (mode == KVM_PAGE_TRACK_WRITE)
>> + if (kvm_mmu_slot_gfn_write_protect(kvm, slot, gfn))
>> + kvm_flush_remote_tlbs(kvm);
>> +}
>> +
>> /*
>> * add guest page to the tracking pool so that corresponding access
>> on that
>> * page will be intercepted.
>> @@ -101,21 +121,27 @@ void kvm_page_track_add_page(struct kvm *kvm,
>> gfn_t gfn,
>> slot = __gfn_to_memslot(slots, gfn);
>> spin_lock(&kvm->mmu_lock);
>> - update_gfn_track(slot, gfn, mode, 1);
>> -
>> - /*
>> - * new track stops large page mapping for the
>> - * tracked page.
>> - */
>> - kvm_mmu_gfn_disallow_lpage(slot, gfn);
>> -
>> - if (mode == KVM_PAGE_TRACK_WRITE)
>> - if (kvm_mmu_slot_gfn_write_protect(kvm, slot, gfn))
>> - kvm_flush_remote_tlbs(kvm);
>> + kvm_slot_page_track_add_page_nolock(kvm, slot, gfn, mode);
>> spin_unlock(&kvm->mmu_lock);
>> }
>> }
>> +void kvm_slot_page_track_remove_page_nolock(struct kvm *kvm,
>> + struct kvm_memory_slot *slot,
>> + gfn_t gfn,
>> + enum kvm_page_track_mode mode)
>> +{
>> + WARN_ON(!check_mode(mode));
>> +
>> + update_gfn_track(slot, gfn, mode, -1);
>> +
>> + /*
>> + * allow large page mapping for the tracked page
>> + * after the tracker is gone.
>> + */
>> + kvm_mmu_gfn_allow_lpage(slot, gfn);
>> +}
>> +
>> /*
>> * remove the guest page from the tracking pool which stops the
>> interception
>> * of corresponding access on that page. It is the opposed
>> operation of
>> @@ -134,20 +160,12 @@ void kvm_page_track_remove_page(struct kvm
>> *kvm, gfn_t gfn,
>> struct kvm_memory_slot *slot;
>> int i;
>> - WARN_ON(!check_mode(mode));
>> -
>> for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
>> slots = __kvm_memslots(kvm, i);
>> slot = __gfn_to_memslot(slots, gfn);
>> spin_lock(&kvm->mmu_lock);
>> - update_gfn_track(slot, gfn, mode, -1);
>> -
>> - /*
>> - * allow large page mapping for the tracked page
>> - * after the tracker is gone.
>> - */
>> - kvm_mmu_gfn_allow_lpage(slot, gfn);
>> + kvm_slot_page_track_remove_page_nolock(kvm, slot, gfn, mode);
> Looks you need to merge this part with patch 1, as you are modifying
> kvm_page_track_{add,remove}_page here, which are introduced in your
> patch 1.
Should be patch 5. sorry again.
Thanks,
-Kai
>
> Thanks,
> -Kai
>> spin_unlock(&kvm->mmu_lock);
>> }
>> }
>
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