KVM: PPC: Implement correct SID mapping on Book3s_32

Up until now we were doing segment mappings wrong on Book3s_32. For Book3s_64
we were using a trick where we know that a single mmu_context gives us 16 bits
of context ids.

The mm system on Book3s_32 instead uses a clever algorithm to distribute VSIDs
across the available range, so a context id really only gives us 16 available
VSIDs.

To keep at least a few guest processes in the SID shadow, let's map a number of
contexts that we can use as VSID pool. This makes the code be actually correct
and shouldn't hurt performance too much.

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

2 files changed, 35 insertions, 30 deletions

diff --git a/arch/powerpc/kvm/book3s_32_mmu_host.c b/arch/powerpc/kvm/book3s_32_mmu_host.c
index 57dddeb23b9b..9fecbfbce773 100644
--- a/arch/powerpc/kvm/book3s_32_mmu_host.c
+++ b/arch/powerpc/kvm/book3s_32_mmu_host.c
@@ -275,18 +275,15 @@ static struct kvmppc_sid_map *create_sid_map(struct kvm_vcpu *vcpu, u64 gvsid)
         backwards_map = !backwards_map;
 
         /* Uh-oh ... out of mappings. Let's flush! */
-        if (vcpu_book3s->vsid_next >= vcpu_book3s->vsid_max) {
-                vcpu_book3s->vsid_next = vcpu_book3s->vsid_first;
+        if (vcpu_book3s->vsid_next >= VSID_POOL_SIZE) {
+                vcpu_book3s->vsid_next = 0;
                 memset(vcpu_book3s->sid_map, 0,
                        sizeof(struct kvmppc_sid_map) * SID_MAP_NUM);
                 kvmppc_mmu_pte_flush(vcpu, 0, 0);
                 kvmppc_mmu_flush_segments(vcpu);
         }
-        map->host_vsid = vcpu_book3s->vsid_next;
-
-        /* Would have to be 111 to be completely aligned with the rest of
-           Linux, but that is just way too little space! */
-        vcpu_book3s->vsid_next+=1;
+        map->host_vsid = vcpu_book3s->vsid_pool[vcpu_book3s->vsid_next];
+        vcpu_book3s->vsid_next++;
 
         map->guest_vsid = gvsid;
         map->valid = true;
@@ -333,40 +330,38 @@ void kvmppc_mmu_flush_segments(struct kvm_vcpu *vcpu)
 
 void kvmppc_mmu_destroy(struct kvm_vcpu *vcpu)
 {
+        int i;
+
         kvmppc_mmu_hpte_destroy(vcpu);
         preempt_disable();
-        __destroy_context(to_book3s(vcpu)->context_id);
+        for (i = 0; i < SID_CONTEXTS; i++)
+                __destroy_context(to_book3s(vcpu)->context_id[i]);
         preempt_enable();
 }
 
 /* From mm/mmu_context_hash32.c */
-#define CTX_TO_VSID(ctx) (((ctx) * (897 * 16)) & 0xffffff)
+#define CTX_TO_VSID(c, id)      ((((c) * (897 * 16)) + (id * 0x111)) & 0xffffff)
 
 int kvmppc_mmu_init(struct kvm_vcpu *vcpu)
 {
         struct kvmppc_vcpu_book3s *vcpu3s = to_book3s(vcpu);
         int err;
         ulong sdr1;
+        int i;
+        int j;
 
-        err = __init_new_context();
-        if (err < 0)
-                return -1;
-        vcpu3s->context_id = err;
-
-        vcpu3s->vsid_max = CTX_TO_VSID(vcpu3s->context_id + 1) - 1;
-        vcpu3s->vsid_first = CTX_TO_VSID(vcpu3s->context_id);
-
-#if 0 /* XXX still doesn't guarantee uniqueness */
-        /* We could collide with the Linux vsid space because the vsid
-         * wraps around at 24 bits. We're safe if we do our own space
-         * though, so let's always set the highest bit. */
+        for (i = 0; i < SID_CONTEXTS; i++) {
+                err = __init_new_context();
+                if (err < 0)
+                        goto init_fail;
+                vcpu3s->context_id[i] = err;
 
-        vcpu3s->vsid_max |= 0x00800000;
-        vcpu3s->vsid_first |= 0x00800000;
-#endif
-        BUG_ON(vcpu3s->vsid_max < vcpu3s->vsid_first);
+                /* Remember context id for this combination */
+                for (j = 0; j < 16; j++)
+                        vcpu3s->vsid_pool[(i * 16) + j] = CTX_TO_VSID(err, j);
+        }
 
-        vcpu3s->vsid_next = vcpu3s->vsid_first;
+        vcpu3s->vsid_next = 0;
 
         /* Remember where the HTAB is */
         asm ( "mfsdr1 %0" : "=r"(sdr1) );
@@ -376,4 +371,14 @@ int kvmppc_mmu_init(struct kvm_vcpu *vcpu)
         kvmppc_mmu_hpte_init(vcpu);
 
         return 0;
+
+init_fail:
+        for (j = 0; j < i; j++) {
+                if (!vcpu3s->context_id[j])
+                        continue;
+
+                __destroy_context(to_book3s(vcpu)->context_id[j]);
+        }
+
+        return -1;
 }
diff --git a/arch/powerpc/kvm/book3s_64_mmu_host.c b/arch/powerpc/kvm/book3s_64_mmu_host.c
index 4040c8d16ad5..fa2f08434ba5 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_host.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_host.c
@@ -286,7 +286,7 @@ void kvmppc_mmu_flush_segments(struct kvm_vcpu *vcpu)
 void kvmppc_mmu_destroy(struct kvm_vcpu *vcpu)
 {
         kvmppc_mmu_hpte_destroy(vcpu);
-        __destroy_context(to_book3s(vcpu)->context_id);
+        __destroy_context(to_book3s(vcpu)->context_id[0]);
 }
 
 int kvmppc_mmu_init(struct kvm_vcpu *vcpu)
@@ -297,10 +297,10 @@ int kvmppc_mmu_init(struct kvm_vcpu *vcpu)
         err = __init_new_context();
         if (err < 0)
                 return -1;
-        vcpu3s->context_id = err;
+        vcpu3s->context_id[0] = err;
 
-        vcpu3s->vsid_max = ((vcpu3s->context_id + 1) << USER_ESID_BITS) - 1;
-        vcpu3s->vsid_first = vcpu3s->context_id << USER_ESID_BITS;
+        vcpu3s->vsid_max = ((vcpu3s->context_id[0] + 1) << USER_ESID_BITS) - 1;
+        vcpu3s->vsid_first = vcpu3s->context_id[0] << USER_ESID_BITS;
         vcpu3s->vsid_next = vcpu3s->vsid_first;
 
         kvmppc_mmu_hpte_init(vcpu);