Re: [PATCH] KVM: PPC: e500mc: Add support for single threaded vcpus on e6500 core

On Tue, 2014-08-12 at 01:53 +0200, Alexander Graf wrote:

quoted

Am 12.08.2014 um 01:36 schrieb Scott Wood [off-list ref]:

quoted

On Wed, 2014-08-06 at 19:33 +0300, Mihai Caraman wrote:

@@ -390,19 +400,30 @@ static void kvmppc_core_vcpu_free_e500mc(struct kvm_vcpu *vcpu)

static int kvmppc_core_init_vm_e500mc(struct kvm *kvm)
{
-    int lpid;
+    int i, lpid;

-    lpid = kvmppc_alloc_lpid();
-    if (lpid < 0)
-        return lpid;
+    /* The lpid pool supports only 2 entries now */
+    if (threads_per_core > 2)
+        return -ENOMEM;
+
+    /* Each VM allocates one LPID per HW thread index */
+    for (i = 0; i < threads_per_core; i++) {
+        lpid = kvmppc_alloc_lpid();
+        if (lpid < 0)
+            return lpid;
+
+        kvm->arch.lpid_pool[i] = lpid;
+    }

Wouldn't it be simpler to halve the size of the lpid pool that the
allocator sees, and just OR in the high bit based on the low bit of the
cpu number?

Heh, I wrote the same and then removed the section from my reply again. It wouldn't really make that much of a difference if you think it through completely.

But yes, it certainly would be quite a bit more natural. I'm ok either way.

It's not a huge difference, but it would at least get rid of some of the
ifdeffing in the headers.  It'd also be nicer when debugging to have the
LPIDs correlated.

-Scott