File 0097-PPC-spapr-Expose-hypervisor-node-in.patch of Package qemu.3217

From 3c13aafba131dfccaaa684dd2207315f97725bfb Mon Sep 17 00:00:00 2001
From: Alexander Graf <agraf@suse.de>
Date: Thu, 24 Apr 2014 14:57:04 +0200
Subject: [PATCH] PPC: spapr: Expose /hypervisor node in device tree

PR KVM supports an ePAPR compliant hypercall interface in parallel to the
normal sPAPR one. Expose the ePAPR /hypervisor node and properties to the
guest so it can use it.

This enables magic page sharing on PR KVM with -M pseries.

However we had a few nasty bugs in the magic page implementation on vcpus
newer than 970 (p7, p8) that KVM now has workarounds for. It indicates that
it does have these workarounds through the PPC_FIXUP_HCALL capability.

To not expose broken guest kernels to issues on host kernels that don't
have the fixups in place, we don't expose working hypercall instructions
when the fixups are not available so that the guest can never active the
magic page.

Signed-off-by: Alexander Graf <agraf@suse.de>
(cherry picked from commit f7d69146549d717ef6cb5a68a3a4452391416f22)
---
 hw/ppc/spapr.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index f6d22dc..b31c657 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -566,6 +566,26 @@ static void *spapr_create_fdt_skel(hwaddr initrd_base,
     /* event-sources */
     spapr_events_fdt_skel(fdt, epow_irq);
 
+    /* /hypervisor node */
+    if (kvm_enabled()) {
+        uint8_t hypercall[16];
+
+        /* indicate KVM hypercall interface */
+        _FDT((fdt_begin_node(fdt, "hypervisor")));
+        _FDT((fdt_property_string(fdt, "compatible", "linux,kvm")));
+        if (kvmppc_has_cap_fixup_hcalls()) {
+            /*
+             * Older KVM versions with older guest kernels were broken with the
+             * magic page, don't allow the guest to map it.
+             */
+            kvmppc_get_hypercall(first_cpu->env_ptr, hypercall,
+                                 sizeof(hypercall));
+            _FDT((fdt_property(fdt, "hcall-instructions", hypercall,
+                              sizeof(hypercall))));
+        }
+        _FDT((fdt_end_node(fdt)));
+    }
+
     _FDT((fdt_end_node(fdt))); /* close root node */
     _FDT((fdt_finish(fdt)));