[PATCH 2/2] KVM MMU: record reverse mapping for spte only if it's writable

Xiao Guangrong
2010-04-01T08:55:18Z

The read only spte mapping can't hurt shadow page cache,
so, no need to record it.

Using bit9 to record whether the spte is re-mapped

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
arch/x86/kvm/mmu.c | 17 +++++++++++++++--
arch/x86/kvm/mmu.h | 1 +
2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 5de92ae..999f572 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -259,7 +259,17 @@ static int is_dirty_gpte(unsigned long pte)

static int is_rmap_spte(u64 pte)
{
- return is_shadow_present_pte(pte);
+ return pte & PT_RMAP_MASK;
+}
+
+static void spte_set_rmap(u64 *spte)
+{
+ *spte |= PT_RMAP_MASK;
+}
+
+static void spte_clear_rmap(u64 *spte)
+{
+ *spte &= ~PT_RMAP_MASK;
}

static int is_last_spte(u64 pte, int level)
@@ -543,7 +553,7 @@ static int rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
unsigned long *rmapp;
int i, count = 0;

- if (!is_rmap_spte(*spte))
+ if (!is_shadow_present_pte(*spte) || !is_writable_pte(*spte))
return count;
gfn = unalias_gfn(vcpu->kvm, gfn);
sp = page_header(__pa(spte));
@@ -573,6 +583,7 @@ static int rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
;
desc->sptes[i] = spte;
}
+ spte_set_rmap(spte);
return count;
}

@@ -610,6 +621,7 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)

if (!is_rmap_spte(*spte))
return;
+ spte_clear_rmap(spte);
sp = page_header(__pa(spte));
pfn = spte_to_pfn(*spte);
if (*spte & shadow_accessed_mask)
@@ -646,6 +658,7 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
pr_err("rmap_remove: %p %llx many->many\n", spte, *spte);
BUG();
}
+
}

static u64 *rmap_next(struct kvm *kvm, unsigned long *rmapp, u64 *spte)
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index be66759..166b9b5 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -22,6 +22,7 @@
#define PT_PAGE_SIZE_MASK (1ULL << 7)
#define PT_PAT_MASK (1ULL << 7)
#define PT_GLOBAL_MASK (1ULL << 8)
+#define PT_RMAP_MASK (1ULL << 9)
#define PT64_NX_SHIFT 63
#define PT64_NX_MASK (1ULL << PT64_NX_SHIFT)

--
1.6.1.2