KVM: PPC: Make shared struct aka magic page guest endian

The shared (magic) page is a data structure that contains often used
supervisor privileged SPRs accessible via memory to the user to reduce
the number of exits we have to take to read/write them.

When we actually share this structure with the guest we have to maintain
it in guest endianness, because some of the patch tricks only work with
native endian load/store operations.

Since we only share the structure with either host or guest in little
endian on book3s_64 pr mode, we don't have to worry about booke or book3s hv.

For booke, the shared struct stays big endian. For book3s_64 hv we maintain
the struct in host native endian, since it never gets shared with the guest.

For book3s_64 pr we introduce a variable that tells us which endianness the
shared struct is in and route every access to it through helper inline
functions that evaluate this variable.

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

1 files changed, 32 insertions, 1 deletions

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index a9bd0ff..b4e15bf 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -125,6 +125,27 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
 }
 EXPORT_SYMBOL_GPL(kvmppc_prepare_to_enter);
 
+#if defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_KVM_BOOK3S_PR_POSSIBLE)
+static void kvmppc_swab_shared(struct kvm_vcpu *vcpu)
+{
+	struct kvm_vcpu_arch_shared *shared = vcpu->arch.shared;
+	int i;
+
+	shared->sprg0 = swab64(shared->sprg0);
+	shared->sprg1 = swab64(shared->sprg1);
+	shared->sprg2 = swab64(shared->sprg2);
+	shared->sprg3 = swab64(shared->sprg3);
+	shared->srr0 = swab64(shared->srr0);
+	shared->srr1 = swab64(shared->srr1);
+	shared->dar = swab64(shared->dar);
+	shared->msr = swab64(shared->msr);
+	shared->dsisr = swab32(shared->dsisr);
+	shared->int_pending = swab32(shared->int_pending);
+	for (i = 0; i < ARRAY_SIZE(shared->sr); i++)
+		shared->sr[i] = swab32(shared->sr[i]);
+}
+#endif
+
 int kvmppc_kvm_pv(struct kvm_vcpu *vcpu)
 {
 	int nr = kvmppc_get_gpr(vcpu, 11);
@@ -135,7 +156,7 @@ int kvmppc_kvm_pv(struct kvm_vcpu *vcpu)
 	unsigned long __maybe_unused param4 = kvmppc_get_gpr(vcpu, 6);
 	unsigned long r2 = 0;
 
-	if (!(vcpu->arch.shared->msr & MSR_SF)) {
+	if (!(kvmppc_get_msr(vcpu) & MSR_SF)) {
 		/* 32 bit mode */
 		param1 &= 0xffffffff;
 		param2 &= 0xffffffff;
@@ -146,6 +167,16 @@ int kvmppc_kvm_pv(struct kvm_vcpu *vcpu)
 	switch (nr) {
 	case KVM_HCALL_TOKEN(KVM_HC_PPC_MAP_MAGIC_PAGE):
 	{
+#if defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_KVM_BOOK3S_PR_POSSIBLE)
+		/* Book3S can be little endian, find it out here */
+		int shared_big_endian = true;
+		if (vcpu->arch.intr_msr & MSR_LE)
+			shared_big_endian = false;
+		if (shared_big_endian != vcpu->arch.shared_big_endian)
+			kvmppc_swab_shared(vcpu);
+		vcpu->arch.shared_big_endian = shared_big_endian;
+#endif
+
 		vcpu->arch.magic_page_pa = param1;
 		vcpu->arch.magic_page_ea = param2;