KVM: PPC: Add an interface for pinning guest pages in Book3s HV guests

This adds two new functions, kvmppc_pin_guest_page() and
kvmppc_unpin_guest_page(), and uses them to pin the guest pages where
the guest has registered areas of memory for the hypervisor to update,
(i.e. the per-cpu virtual processor areas, SLB shadow buffers and
dispatch trace logs) and then unpin them when they are no longer
required.

Although it is not strictly necessary to pin the pages at this point,
since all guest pages are already pinned, later commits in this series
will mean that guest pages aren't all pinned.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index e4c60698f41a..dcd39dc64f07 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -184,6 +184,44 @@ static int kvmppc_mmu_book3s_64_hv_xlate(struct kvm_vcpu *vcpu, gva_t eaddr,
 	return -ENOENT;
 }
 
+void *kvmppc_pin_guest_page(struct kvm *kvm, unsigned long gpa,
+			    unsigned long *nb_ret)
+{
+	struct kvm_memory_slot *memslot;
+	unsigned long gfn = gpa >> PAGE_SHIFT;
+	struct page *page;
+	unsigned long offset;
+	unsigned long pfn, pa;
+	unsigned long *physp;
+
+	memslot = gfn_to_memslot(kvm, gfn);
+	if (!memslot || (memslot->flags & KVM_MEMSLOT_INVALID))
+		return NULL;
+	physp = kvm->arch.slot_phys[memslot->id];
+	if (!physp)
+		return NULL;
+	physp += (gfn - memslot->base_gfn) >>
+		(kvm->arch.ram_porder - PAGE_SHIFT);
+	pa = *physp;
+	if (!pa)
+		return NULL;
+	pfn = pa >> PAGE_SHIFT;
+	page = pfn_to_page(pfn);
+	get_page(page);
+	offset = gpa & (kvm->arch.ram_psize - 1);
+	if (nb_ret)
+		*nb_ret = kvm->arch.ram_psize - offset;
+	return page_address(page) + offset;
+}
+
+void kvmppc_unpin_guest_page(struct kvm *kvm, void *va)
+{
+	struct page *page = virt_to_page(va);
+
+	page = compound_head(page);
+	put_page(page);
+}
+
 void kvmppc_mmu_book3s_hv_init(struct kvm_vcpu *vcpu)
 {
 	struct kvmppc_mmu *mmu = &vcpu->arch.mmu;