KVM: PPC: PV mtmsrd L=1
The PowerPC ISA has a special instruction for mtmsr that only changes the EE
and RI bits, namely the L=1 form.
Since that one is reasonably often occuring and simple to implement, let's
go with this first. Writing EE=0 is always just a store. Doing EE=1 also
requires us to check for pending interrupts and if necessary exit back to the
hypervisor.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/powerpc/kernel/kvm.c b/arch/powerpc/kernel/kvm.c
index 239a70d..717ab0d 100644
--- a/arch/powerpc/kernel/kvm.c
+++ b/arch/powerpc/kernel/kvm.c
@@ -63,6 +63,7 @@
#define KVM_INST_MTSPR_DSISR 0x7c1203a6
#define KVM_INST_TLBSYNC 0x7c00046c
+#define KVM_INST_MTMSRD_L1 0x7c010164
static bool kvm_patching_worked = true;
static char kvm_tmp[1024 * 1024];
@@ -138,6 +139,43 @@
return p;
}
+extern u32 kvm_emulate_mtmsrd_branch_offs;
+extern u32 kvm_emulate_mtmsrd_reg_offs;
+extern u32 kvm_emulate_mtmsrd_len;
+extern u32 kvm_emulate_mtmsrd[];
+
+static void kvm_patch_ins_mtmsrd(u32 *inst, u32 rt)
+{
+ u32 *p;
+ int distance_start;
+ int distance_end;
+ ulong next_inst;
+
+ p = kvm_alloc(kvm_emulate_mtmsrd_len * 4);
+ if (!p)
+ return;
+
+ /* Find out where we are and put everything there */
+ distance_start = (ulong)p - (ulong)inst;
+ next_inst = ((ulong)inst + 4);
+ distance_end = next_inst - (ulong)&p[kvm_emulate_mtmsrd_branch_offs];
+
+ /* Make sure we only write valid b instructions */
+ if (distance_start > KVM_INST_B_MAX) {
+ kvm_patching_worked = false;
+ return;
+ }
+
+ /* Modify the chunk to fit the invocation */
+ memcpy(p, kvm_emulate_mtmsrd, kvm_emulate_mtmsrd_len * 4);
+ p[kvm_emulate_mtmsrd_branch_offs] |= distance_end & KVM_INST_B_MASK;
+ p[kvm_emulate_mtmsrd_reg_offs] |= rt;
+ flush_icache_range((ulong)p, (ulong)p + kvm_emulate_mtmsrd_len * 4);
+
+ /* Patch the invocation */
+ kvm_patch_ins_b(inst, distance_start);
+}
+
static void kvm_map_magic_page(void *data)
{
kvm_hypercall2(KVM_HC_PPC_MAP_MAGIC_PAGE,
@@ -211,6 +249,13 @@
case KVM_INST_TLBSYNC:
kvm_patch_ins_nop(inst);
break;
+
+ /* Rewrites */
+ case KVM_INST_MTMSRD_L1:
+ /* We use r30 and r31 during the hook */
+ if (get_rt(inst_rt) < 30)
+ kvm_patch_ins_mtmsrd(inst, inst_rt);
+ break;
}
switch (_inst) {