KVM: PPC: Book3S: Make magic page properly 4k mappable

The magic page is defined as a 4k page of per-vCPU data that is shared
between the guest and the host to accelerate accesses to privileged
registers.

However, when the host is using 64k page size granularity we weren't quite
as strict about that rule anymore. Instead, we partially treated all of the
upper 64k as magic page and mapped only the uppermost 4k with the actual
magic contents.

This works well enough for Linux which doesn't use any memory in kernel
space in the upper 64k, but Mac OS X got upset. So this patch makes magic
page actually stay in a 4k range even on 64k page size hosts.

This patch fixes magic page usage with Mac OS X (using MOL) on 64k PAGE_SIZE
hosts for me.

Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 19 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 7efc2b7..fe0257a 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -190,6 +190,25 @@ int kvmppc_kvm_pv(struct kvm_vcpu *vcpu)
 		vcpu->arch.magic_page_pa = param1 & ~0xfffULL;
 		vcpu->arch.magic_page_ea = param2 & ~0xfffULL;
 
+#ifdef CONFIG_PPC_64K_PAGES
+		/*
+		 * Make sure our 4k magic page is in the same window of a 64k
+		 * page within the guest and within the host's page.
+		 */
+		if ((vcpu->arch.magic_page_pa & 0xf000) !=
+		    ((ulong)vcpu->arch.shared & 0xf000)) {
+			void *old_shared = vcpu->arch.shared;
+			ulong shared = (ulong)vcpu->arch.shared;
+			void *new_shared;
+
+			shared &= PAGE_MASK;
+			shared |= vcpu->arch.magic_page_pa & 0xf000;
+			new_shared = (void*)shared;
+			memcpy(new_shared, old_shared, 0x1000);
+			vcpu->arch.shared = new_shared;
+		}
+#endif
+
 		r2 = KVM_MAGIC_FEAT_SR | KVM_MAGIC_FEAT_MAS0_TO_SPRG7;
 
 		r = EV_SUCCESS;