[PATCH v2 30/33] KVM: PPC: Book3S HV: Handle differing endianness for H_ENTER_NESTED

[Paul Mackerras]

From: Suraj Jitindar Singh <sjitindarsingh at gmail.com>

The hcall H_ENTER_NESTED takes as the two parameters the address in
L1 guest memory of a hv_regs struct and a pt_regs struct which the
L1 guest would like to use to run a L2 guest and in which are returned
the exit state of the L2 guest.  For efficiency, these are in the
endianness of the L1 guest, rather than being always big-endian as is
usually the case for PAPR hypercalls.

When reading/writing these structures, this patch handles the case
where the endianness of the L1 guest differs from that of the L0
hypervisor, by byteswapping the structures after reading and before
writing them back.

Since all the fields of the pt_regs are of the same type, i.e.,
unsigned long, we treat it as an array of unsigned longs.  The fields
of struct hv_guest_state are not all the same, so its fields are
byteswapped individually.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh at gmail.com>
Signed-off-by: Paul Mackerras <paulus at ozlabs.org>
---
 arch/powerpc/kvm/book3s_hv_nested.c | 51 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 50 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
index c3fb171..8199908 100644
--- a/arch/powerpc/kvm/book3s_hv_nested.c
+++ b/arch/powerpc/kvm/book3s_hv_nested.c
@@ -51,6 +51,48 @@ void kvmhv_save_hv_regs(struct kvm_vcpu *vcpu, struct hv_guest_state *hr)
 	hr->ppr = vcpu->arch.ppr;
 }
 
+static void byteswap_pt_regs(struct pt_regs *regs)
+{
+	unsigned long *addr = (unsigned long *) regs;
+
+	for (; addr < ((unsigned long *) (regs + 1)); addr++)
+		*addr = swab64(*addr);
+}
+
+static void byteswap_hv_regs(struct hv_guest_state *hr)
+{
+	hr->version = swab64(hr->version);
+	hr->lpid = swab32(hr->lpid);
+	hr->vcpu_token = swab32(hr->vcpu_token);
+	hr->lpcr = swab64(hr->lpcr);
+	hr->pcr = swab64(hr->pcr);
+	hr->amor = swab64(hr->amor);
+	hr->dpdes = swab64(hr->dpdes);
+	hr->hfscr = swab64(hr->hfscr);
+	hr->tb_offset = swab64(hr->tb_offset);
+	hr->dawr0 = swab64(hr->dawr0);
+	hr->dawrx0 = swab64(hr->dawrx0);
+	hr->ciabr = swab64(hr->ciabr);
+	hr->hdec_expiry = swab64(hr->hdec_expiry);
+	hr->purr = swab64(hr->purr);
+	hr->spurr = swab64(hr->spurr);
+	hr->ic = swab64(hr->ic);
+	hr->vtb = swab64(hr->vtb);
+	hr->hdar = swab64(hr->hdar);
+	hr->hdsisr = swab64(hr->hdsisr);
+	hr->heir = swab64(hr->heir);
+	hr->asdr = swab64(hr->asdr);
+	hr->srr0 = swab64(hr->srr0);
+	hr->srr1 = swab64(hr->srr1);
+	hr->sprg[0] = swab64(hr->sprg[0]);
+	hr->sprg[1] = swab64(hr->sprg[1]);
+	hr->sprg[2] = swab64(hr->sprg[2]);
+	hr->sprg[3] = swab64(hr->sprg[3]);
+	hr->pidr = swab64(hr->pidr);
+	hr->cfar = swab64(hr->cfar);
+	hr->ppr = swab64(hr->ppr);
+}
+
 static void save_hv_return_state(struct kvm_vcpu *vcpu, int trap,
 				 struct hv_guest_state *hr)
 {
@@ -175,6 +217,8 @@ long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu)
 				  sizeof(struct hv_guest_state));
 	if (err)
 		return H_PARAMETER;
+	if (kvmppc_need_byteswap(vcpu))
+		byteswap_hv_regs(&l2_hv);
 	if (l2_hv.version != HV_GUEST_STATE_VERSION)
 		return H_P2;
 
@@ -183,7 +227,8 @@ long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu)
 				  sizeof(struct pt_regs));
 	if (err)
 		return H_PARAMETER;
-
+	if (kvmppc_need_byteswap(vcpu))
+		byteswap_pt_regs(&l2_regs);
 	if (l2_hv.vcpu_token >= NR_CPUS)
 		return H_PARAMETER;
 
@@ -255,6 +300,10 @@ long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu)
 	kvmhv_put_nested(l2);
 
 	/* copy l2_hv_state and regs back to guest */
+	if (kvmppc_need_byteswap(vcpu)) {
+		byteswap_hv_regs(&l2_hv);
+		byteswap_pt_regs(&l2_regs);
+	}
 	err = kvm_vcpu_write_guest(vcpu, hv_ptr, &l2_hv,
 				   sizeof(struct hv_guest_state));
 	if (err)
-- 
2.7.4