Re: [PATCH v2] xen: Allow CPU to be counted than currently "plugged".

[Ian Campbell <Ian.Campbell@citrix.com>]

On Mon, 2013-06-17 at 15:22 +0100, Anthony PERARD wrote:
> Under Xen, SeaBIOS can count more CPU than there should be. This patch
> will allow more CPU to come up instead of going to infinite loop waiting
> for the CPU counter to be decremented.

Current upstream SeaBIOS has this very different and only runs this loop
on Qemu.

At a minimum I think we would need to backport:
        5dbf173 Only perform SMP setup on QEMU.
        897fb11 Consistently use CONFIG_COREBOOT, CONFIG_QEMU, and runningOnXen().

We've currently got SeaBIOS 1.7.1 in our tree and these are only in the
master branch, but I think backporting is the way to go.

Hrm, 897fb11 doesn't backport cleanly (lots of changes) and without it
5dbf173 doesn't backport cleanly either. But I think the net affect when
running on Xen would be the same as the following, can you try it?

diff --git a/src/smp.c b/src/smp.c
index 3c36f8c..fb55a6e 100644
--- a/src/smp.c
+++ b/src/smp.c
@@ -84,6 +84,9 @@ int apic_id_is_present(u8 apic_id)
 void
 smp_probe(void)
 {
+    if (usingXen())
+        return;
+
     ASSERT32FLAT();
     u32 eax, ebx, ecx, cpuid_features;
     cpuid(1, &eax, &ebx, &ecx, &cpuid_features);