[Xen-devel] [PATCH] tools/libxc: disable x2APIC when using nested virtualization

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

There are issues (as reported by osstest [0]) when Xen is running
nested on itself and the L1 Xen is using x2APIC. While those are being
investigated, disable announcing the x2APIC feature in CPUID when
nested HVM mode is enabled.

[0] http://logs.test-lab.xenproject.org/osstest/logs/145509/

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 tools/libxc/xc_cpuid_x86.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/tools/libxc/xc_cpuid_x86.c b/tools/libxc/xc_cpuid_x86.c
index 2540aa1e1c..ac38c1406e 100644
--- a/tools/libxc/xc_cpuid_x86.c
+++ b/tools/libxc/xc_cpuid_x86.c
@@ -653,6 +653,17 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t 
domid,
         p->extd.itsc = true;
         p->basic.vmx = true;
         p->extd.svm = true;
+
+        /*
+         * BODGE: don't announce x2APIC mode when using nested virtualization,
+         * as it doesn't work properly. This should be removed once the
+         * underlying bug(s) are fixed.
+         */
+        rc = xc_hvm_param_get(xch, domid, HVM_PARAM_NESTEDHVM, &val);
+        if ( rc )
+            goto out;
+        if ( val )
+            p->basic.x2apic = false;
     }
 
     rc = x86_cpuid_copy_to_buffer(p, leaves, &nr_leaves);
-- 
2.24.1


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