[PATCH 1/3] KVM: PPC: Implement kvmppc_copy_guest() to perform in place copy of guest memory

[Suraj Jitindar Singh <sjitindarsingh@gmail.com>]

Implement the function kvmppc_copy_guest() to be used to perform a memory
copy from one guest physical address to another of a variable length.

This performs similar functionality as the kvm_read_guest() and
kvm_write_guest() functions, except both addresses point to guest memory.
This performs a copy in place using raw_copy_in_user() to avoid having to
buffer the data.

The guest memory can reside in different memslots and the copy length
can span memslots.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
---
 arch/powerpc/kvm/book3s_hv.c | 69 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index ec38576dc685..7179ea783f4f 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -814,6 +814,75 @@ static int kvmppc_h_set_mode(struct kvm_vcpu *vcpu, unsigned long mflags,
 	}
 }
 
+static int __kvmppc_copy_guest_page(struct kvm_memory_slot *to_memslot,
+				    gfn_t to_gfn, int to_offset,
+				    struct kvm_memory_slot *from_memslot,
+				    gfn_t from_gfn, int from_offset, int len)
+{
+	int r;
+	unsigned long to_addr, from_addr;
+
+	to_addr = gfn_to_hva_memslot(to_memslot, to_gfn);
+	if (kvm_is_error_hva(to_addr))
+		return -EFAULT;
+	from_addr = gfn_to_hva_memslot(from_memslot, from_gfn);
+	if (kvm_is_error_hva(from_addr))
+		return -EFAULT;
+	r = raw_copy_in_user((void __user *)to_addr + to_offset,
+			     (void __user *)from_addr + from_offset, len);
+	if (r)
+		return -EFAULT;
+	return 0;
+}
+
+static int next_segment_many(unsigned long len, int offset1, int offset2)
+{
+	int size = min(PAGE_SIZE - offset1, PAGE_SIZE - offset2);
+
+	if (len > size)
+		return size;
+	else
+		return len;
+}
+
+static int kvmppc_copy_guest(struct kvm *kvm, gpa_t to, gpa_t from,
+			     unsigned long len)
+{
+	struct kvm_memory_slot *to_memslot = NULL;
+	struct kvm_memory_slot *from_memslot = NULL;
+	gfn_t to_gfn = to >> PAGE_SHIFT;
+	gfn_t from_gfn = from >> PAGE_SHIFT;
+	int seg;
+	int to_offset = offset_in_page(to);
+	int from_offset = offset_in_page(from);
+	int ret;
+
+	while ((seg = next_segment_many(len, to_offset, from_offset)) != 0) {
+		if (!to_memslot || (to_gfn >= (to_memslot->base_gfn +
+					       to_memslot->npages)))
+			to_memslot = gfn_to_memslot(kvm, to_gfn);
+		if (!from_memslot || (from_gfn >= (from_memslot->base_gfn +
+						   from_memslot->npages)))
+			from_memslot = gfn_to_memslot(kvm, from_gfn);
+
+		ret = __kvmppc_copy_guest_page(to_memslot, to_gfn, to_offset,
+					       from_memslot, from_gfn,
+					       from_offset, seg);
+		if (ret < 0)
+			return ret;
+		mark_page_dirty(kvm, to_gfn);
+
+		to_offset = (to_offset + seg) & (PAGE_SIZE - 1);
+		from_offset = (from_offset + seg) & (PAGE_SIZE - 1);
+		len -= seg;
+		if (!to_offset)
+			to_gfn += 1;
+		if (!from_offset)
+			from_gfn += 1;
+	}
+	return 0;
+}
+
 static int kvm_arch_vcpu_yield_to(struct kvm_vcpu *target)
 {
 	struct kvmppc_vcore *vcore = target->arch.vcore;
-- 
2.13.6