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FromAvi Kivity <>
Subject[PATCH 26/39] KVM: MMU: Add generic shadow walker
DateThu, 25 Sep 2008 14:54:58 +0300
From: Avi Kivity <avi@qumranet.com>

We currently walk the shadow page tables in two places: direct map (for
real mode and two dimensional paging) and paging mode shadow. Since we
anticipate requiring a third walk (for invlpg), it makes sense to have
a generic facility for shadow walk.

This patch adds such a shadow walker, walks the page tables and calls a
method for every spte encountered. The method can examine the spte,
modify it, or even instantiate it. The walk can be aborted by returning
nonzero from the method.

Signed-off-by: Avi Kivity <avi@qumranet.com>
---
arch/x86/kvm/mmu.c | 34 ++++++++++++++++++++++++++++++++++
1 files changed, 34 insertions(+), 0 deletions(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 72f739a..8b95cf7 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -142,6 +142,11 @@ struct kvm_rmap_desc {
struct kvm_rmap_desc *more;
};

+struct kvm_shadow_walk {
+ int (*entry)(struct kvm_shadow_walk *walk, struct kvm_vcpu *vcpu,
+ gva_t addr, u64 *spte, int level);
+};
+
static struct kmem_cache *pte_chain_cache;
static struct kmem_cache *rmap_desc_cache;
static struct kmem_cache *mmu_page_header_cache;
@@ -935,6 +940,35 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
return sp;
}

+static int walk_shadow(struct kvm_shadow_walk *walker,
+ struct kvm_vcpu *vcpu, gva_t addr)
+{
+ hpa_t shadow_addr;
+ int level;
+ int r;
+ u64 *sptep;
+ unsigned index;
+
+ shadow_addr = vcpu->arch.mmu.root_hpa;
+ level = vcpu->arch.mmu.shadow_root_level;
+ if (level == PT32E_ROOT_LEVEL) {
+ shadow_addr = vcpu->arch.mmu.pae_root[(addr >> 30) & 3];
+ shadow_addr &= PT64_BASE_ADDR_MASK;
+ --level;
+ }
+
+ while (level >= PT_PAGE_TABLE_LEVEL) {
+ index = SHADOW_PT_INDEX(addr, level);
+ sptep = ((u64 *)__va(shadow_addr)) + index;
+ r = walker->entry(walker, vcpu, addr, sptep, level);
+ if (r)
+ return r;
+ shadow_addr = *sptep & PT64_BASE_ADDR_MASK;
+ --level;
+ }
+ return 0;
+}
+
static void kvm_mmu_page_unlink_children(struct kvm *kvm,
struct kvm_mmu_page *sp)
{
--
1.6.0.1


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