KVM: Lazy guest cr3 switching
Switch guest paging context may require us to allocate memory, which
might fail. Instead of wiring up error paths everywhere, make context
switching lazy and actually do the switch before the next guest entry,
where we can return an error if allocation fails.
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index 283df03..5915d7a 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -949,9 +949,7 @@
context->free = nonpaging_free;
context->root_level = 0;
context->shadow_root_level = PT32E_ROOT_LEVEL;
- mmu_alloc_roots(vcpu);
- ASSERT(VALID_PAGE(context->root_hpa));
- kvm_arch_ops->set_cr3(vcpu, context->root_hpa);
+ context->root_hpa = INVALID_PAGE;
return 0;
}
@@ -965,11 +963,6 @@
{
pgprintk("%s: cr3 %lx\n", __FUNCTION__, vcpu->cr3);
mmu_free_roots(vcpu);
- if (unlikely(vcpu->kvm->n_free_mmu_pages < KVM_MIN_FREE_MMU_PAGES))
- kvm_mmu_free_some_pages(vcpu);
- mmu_alloc_roots(vcpu);
- kvm_mmu_flush_tlb(vcpu);
- kvm_arch_ops->set_cr3(vcpu, vcpu->mmu.root_hpa);
}
static void inject_page_fault(struct kvm_vcpu *vcpu,
@@ -1003,10 +996,7 @@
context->free = paging_free;
context->root_level = level;
context->shadow_root_level = level;
- mmu_alloc_roots(vcpu);
- ASSERT(VALID_PAGE(context->root_hpa));
- kvm_arch_ops->set_cr3(vcpu, context->root_hpa |
- (vcpu->cr3 & (CR3_PCD_MASK | CR3_WPT_MASK)));
+ context->root_hpa = INVALID_PAGE;
return 0;
}
@@ -1025,10 +1015,7 @@
context->free = paging_free;
context->root_level = PT32_ROOT_LEVEL;
context->shadow_root_level = PT32E_ROOT_LEVEL;
- mmu_alloc_roots(vcpu);
- ASSERT(VALID_PAGE(context->root_hpa));
- kvm_arch_ops->set_cr3(vcpu, context->root_hpa |
- (vcpu->cr3 & (CR3_PCD_MASK | CR3_WPT_MASK)));
+ context->root_hpa = INVALID_PAGE;
return 0;
}
@@ -1042,7 +1029,6 @@
ASSERT(vcpu);
ASSERT(!VALID_PAGE(vcpu->mmu.root_hpa));
- mmu_topup_memory_caches(vcpu);
if (!is_paging(vcpu))
return nonpaging_init_context(vcpu);
else if (is_long_mode(vcpu))
@@ -1064,16 +1050,31 @@
int kvm_mmu_reset_context(struct kvm_vcpu *vcpu)
{
+ destroy_kvm_mmu(vcpu);
+ return init_kvm_mmu(vcpu);
+}
+
+int kvm_mmu_load(struct kvm_vcpu *vcpu)
+{
int r;
- destroy_kvm_mmu(vcpu);
- r = init_kvm_mmu(vcpu);
- if (r < 0)
- goto out;
+ spin_lock(&vcpu->kvm->lock);
r = mmu_topup_memory_caches(vcpu);
+ if (r)
+ goto out;
+ mmu_alloc_roots(vcpu);
+ kvm_arch_ops->set_cr3(vcpu, vcpu->mmu.root_hpa);
+ kvm_mmu_flush_tlb(vcpu);
out:
+ spin_unlock(&vcpu->kvm->lock);
return r;
}
+EXPORT_SYMBOL_GPL(kvm_mmu_load);
+
+void kvm_mmu_unload(struct kvm_vcpu *vcpu)
+{
+ mmu_free_roots(vcpu);
+}
static void mmu_pte_write_zap_pte(struct kvm_vcpu *vcpu,
struct kvm_mmu_page *page,