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Date: Tue, 15 Dec 2015 15:52:24 +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 12/01/2015 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.
Thanks,
-Kai
> spin_unlock(&kvm->mmu_lock);
> }
> }
--
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