KVM: PPC: Magic Page Book3s support

We need to override EA as well as PA lookups for the magic page. When the guest
tells us to project it, the magic page overrides any guest mappings.

In order to reflect that, we need to hook into all the MMU layers of KVM to
force map the magic page if necessary.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 32 insertions, 3 deletions

diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index 0ed5376df82c..eee97b5a7400 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -419,6 +419,25 @@ void kvmppc_set_pvr(struct kvm_vcpu *vcpu, u32 pvr)
 	}
 }
 
+pfn_t kvmppc_gfn_to_pfn(struct kvm_vcpu *vcpu, gfn_t gfn)
+{
+	ulong mp_pa = vcpu->arch.magic_page_pa;
+
+	/* Magic page override */
+	if (unlikely(mp_pa) &&
+	    unlikely(((gfn << PAGE_SHIFT) & KVM_PAM) ==
+		     ((mp_pa & PAGE_MASK) & KVM_PAM))) {
+		ulong shared_page = ((ulong)vcpu->arch.shared) & PAGE_MASK;
+		pfn_t pfn;
+
+		pfn = (pfn_t)virt_to_phys((void*)shared_page) >> PAGE_SHIFT;
+		get_page(pfn_to_page(pfn));
+		return pfn;
+	}
+
+	return gfn_to_pfn(vcpu->kvm, gfn);
+}
+
 /* Book3s_32 CPUs always have 32 bytes cache line size, which Linux assumes. To
  * make Book3s_32 Linux work on Book3s_64, we have to make sure we trap dcbz to
  * emulate 32 bytes dcbz length.
@@ -554,6 +573,13 @@ mmio:
 
 static int kvmppc_visible_gfn(struct kvm_vcpu *vcpu, gfn_t gfn)
 {
+	ulong mp_pa = vcpu->arch.magic_page_pa;
+
+	if (unlikely(mp_pa) &&
+	    unlikely((mp_pa & KVM_PAM) >> PAGE_SHIFT == gfn)) {
+		return 1;
+	}
+
 	return kvm_is_visible_gfn(vcpu->kvm, gfn);
 }
 
@@ -1257,6 +1283,7 @@ struct kvm_vcpu *kvmppc_core_vcpu_create(struct kvm *kvm, unsigned int id)
 	struct kvmppc_vcpu_book3s *vcpu_book3s;
 	struct kvm_vcpu *vcpu;
 	int err = -ENOMEM;
+	unsigned long p;
 
 	vcpu_book3s = vmalloc(sizeof(struct kvmppc_vcpu_book3s));
 	if (!vcpu_book3s)
@@ -1274,8 +1301,10 @@ struct kvm_vcpu *kvmppc_core_vcpu_create(struct kvm *kvm, unsigned int id)
 	if (err)
 		goto free_shadow_vcpu;
 
-	vcpu->arch.shared = (void*)__get_free_page(GFP_KERNEL|__GFP_ZERO);
-	if (!vcpu->arch.shared)
+	p = __get_free_page(GFP_KERNEL|__GFP_ZERO);
+	/* the real shared page fills the last 4k of our page */
+	vcpu->arch.shared = (void*)(p + PAGE_SIZE - 4096);
+	if (!p)
 		goto uninit_vcpu;
 
 	vcpu->arch.host_retip = kvm_return_point;
@@ -1322,7 +1351,7 @@ void kvmppc_core_vcpu_free(struct kvm_vcpu *vcpu)
 {
 	struct kvmppc_vcpu_book3s *vcpu_book3s = to_book3s(vcpu);
 
-	free_page((unsigned long)vcpu->arch.shared);
+	free_page((unsigned long)vcpu->arch.shared & PAGE_MASK);
 	kvm_vcpu_uninit(vcpu);
 	kfree(vcpu_book3s->shadow_vcpu);
 	vfree(vcpu_book3s);