Prev: [PATCH v2 1/3] KVM: MMU: using kvm_set_pfn_accessed() instead of mark_page_accessed()
Next: [PATCH v2 2/3] KVM: MMU: move bits lost judgement into a separate function
From: Xiao Guangrong on 2 Aug 2010 04:20
Mark page dirty only when this page is really written, it's more exacter,
and also can fix dirty page marking in speculation path

Signed-off-by: Xiao Guangrong <xiaoguangrong(a)cn.fujitsu.com>
---
arch/x86/kvm/mmu.c | 47 ++++++++++++++++++++++++++++-------------------
1 files changed, 28 insertions(+), 19 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index e18834c..9c69725 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -311,24 +311,42 @@ static bool spte_has_volatile_bits(u64 spte)
if (!is_shadow_present_pte(spte))
return false;

- if (spte & shadow_accessed_mask)
+ if ((spte & shadow_accessed_mask) &&
+ (!is_writable_pte(spte) || (spte & shadow_dirty_mask)))
return false;

return true;
}

+static bool spte_is_bit_cleared(u64 old_spte, u64 new_spte, u64 bit_mask)
+{
+ return (old_spte & bit_mask) && !(new_spte & bit_mask);
+}
+
static void update_spte(u64 *sptep, u64 new_spte)
{
- u64 old_spte;
+ u64 mask, old_spte = *sptep;
+
+ WARN_ON(!is_rmap_spte(new_spte));

- if (!shadow_accessed_mask || (new_spte & shadow_accessed_mask) ||
- !is_rmap_spte(*sptep))
+ new_spte |= old_spte & shadow_dirty_mask;
+
+ mask = shadow_accessed_mask;
+ if (is_writable_pte(old_spte))
+ mask |= shadow_dirty_mask;
+
+ if (!spte_has_volatile_bits(old_spte) || (new_spte & mask) == mask)
__set_spte(sptep, new_spte);
- else {
+ else
old_spte = __xchg_spte(sptep, new_spte);
- if (old_spte & shadow_accessed_mask)
- kvm_set_pfn_accessed(spte_to_pfn(old_spte));
- }
+
+ if (!shadow_accessed_mask)
+ return;
+
+ if (spte_is_bit_cleared(old_spte, new_spte, shadow_accessed_mask))
+ kvm_set_pfn_accessed(spte_to_pfn(old_spte));
+ if (spte_is_bit_cleared(old_spte, new_spte, shadow_dirty_mask))
+ kvm_set_pfn_dirty(spte_to_pfn(old_spte));
}

static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
@@ -708,7 +726,7 @@ static void set_spte_track_bits(u64 *sptep, u64 new_spte)
pfn = spte_to_pfn(old_spte);
if (!shadow_accessed_mask || old_spte & shadow_accessed_mask)
kvm_set_pfn_accessed(pfn);
- if (is_writable_pte(old_spte))
+ if (!shadow_dirty_mask || (old_spte & shadow_dirty_mask))
kvm_set_pfn_dirty(pfn);
}

@@ -763,13 +781,6 @@ static int rmap_write_protect(struct kvm *kvm, u64 gfn)
}
spte = rmap_next(kvm, rmapp, spte);
}
- if (write_protected) {
- pfn_t pfn;
-
- spte = rmap_next(kvm, rmapp, NULL);
- pfn = spte_to_pfn(*spte);
- kvm_set_pfn_dirty(pfn);
- }

/* check for huge page mappings */
for (i = PT_DIRECTORY_LEVEL;
@@ -1942,7 +1953,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
* whether the guest actually used the pte (in order to detect
* demand paging).
*/
- spte = shadow_base_present_pte | shadow_dirty_mask;
+ spte = shadow_base_present_pte;
if (!speculative)
spte |= shadow_accessed_mask;
if (!dirty)
@@ -2003,8 +2014,6 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
mark_page_dirty(vcpu->kvm, gfn);

set_pte:
- if (is_writable_pte(*sptep) && !is_writable_pte(spte))
- kvm_set_pfn_dirty(pfn);
update_spte(sptep, spte);
done:
return ret;
--
1.6.1.2


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