Older Xen versions used to expose some CPUID bits which are no longer
exposed by default. In order to keep a compatible behavior with
guests migrated from versions of Xen that don't encode the CPUID data
on the migration stream introduce a function that sets the same bits
as older Xen versions.
This is pulled out from xc_cpuid_apply_policy which already has this
logic present.
No functional change intended.
Signed-off-by: Roger Pau Monné <roger....@citrix.com>
---
Changes since v1:
- Move comments and explicitly mention pre-4.14 Xen.
---
tools/include/xenctrl.h | 4 +++
tools/libs/guest/xg_cpuid_x86.c | 46 ++++++++++++++++++++++++++++-----
2 files changed, 43 insertions(+), 7 deletions(-)
diff --git a/tools/include/xenctrl.h b/tools/include/xenctrl.h
index c41d794683c..89a73fd6823 100644
--- a/tools/include/xenctrl.h
+++ b/tools/include/xenctrl.h
@@ -2627,6 +2627,10 @@ int xc_cpu_policy_calc_compatible(xc_interface *xch,
const xc_cpu_policy_t p2,
xc_cpu_policy_t out);
+/* Make a policy compatible with pre-4.14 Xen versions. */
+int xc_cpu_policy_make_compatible(xc_interface *xch, xc_cpu_policy_t policy,
+ bool hvm);
+
int xc_get_cpu_levelling_caps(xc_interface *xch, uint32_t *caps);
int xc_get_cpu_featureset(xc_interface *xch, uint32_t index,
uint32_t *nr_features, uint32_t *featureset);
diff --git a/tools/libs/guest/xg_cpuid_x86.c b/tools/libs/guest/xg_cpuid_x86.c
index 6cfa4cb39d1..6486ac4c673 100644
--- a/tools/libs/guest/xg_cpuid_x86.c
+++ b/tools/libs/guest/xg_cpuid_x86.c
@@ -446,6 +446,7 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t
domid, bool restore,
unsigned int i, nr_leaves, nr_msrs;
xen_cpuid_leaf_t *leaves = NULL;
struct cpuid_policy *p = NULL;
+ struct xc_cpu_policy policy = { };
uint32_t err_leaf = -1, err_subleaf = -1, err_msr = -1;
uint32_t host_featureset[FEATURESET_NR_ENTRIES] = {};
uint32_t len = ARRAY_SIZE(host_featureset);
@@ -509,17 +510,14 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t
domid, bool restore,
}
/*
- * Account for feature which have been disabled by default since Xen 4.13,
+ * Account for features which have been disabled by default since Xen 4.13,
* so migrated-in VM's don't risk seeing features disappearing.
*/
if ( restore )
{
- p->basic.rdrand = test_bit(X86_FEATURE_RDRAND, host_featureset);
-
- if ( di.hvm )
- {
- p->feat.mpx = test_bit(X86_FEATURE_MPX, host_featureset);
- }
+ policy.cpuid = *p;
+ xc_cpu_policy_make_compatible(xch, &policy, di.hvm);
+ *p = policy.cpuid;
}
if ( featureset )
@@ -1072,3 +1070,37 @@ int xc_cpu_policy_calc_compatible(xc_interface *xch,
return rc;
}
+
+int xc_cpu_policy_make_compatible(xc_interface *xch, xc_cpu_policy_t policy,
+ bool hvm)
+{
+ xc_cpu_policy_t host;
+ int rc;
+
+ host = xc_cpu_policy_init();
+ if ( !host )
+ {
+ errno = ENOMEM;
+ return -1;
+ }
+
+ rc = xc_cpu_policy_get_system(xch, XEN_SYSCTL_cpu_policy_host, host);
+ if ( rc )
+ {
+ ERROR("Failed to get host policy");
+ goto out;
+ }
+
+ /*
+ * Account for features which have been disabled by default since Xen 4.13,
+ * so migrated-in VM's don't risk seeing features disappearing.
+ */
+ policy->cpuid.basic.rdrand = host->cpuid.basic.rdrand;
+
+ if ( hvm )
+ policy->cpuid.feat.mpx = host->cpuid.feat.mpx;
+
+ out:
+ xc_cpu_policy_destroy(host);
+ return rc;
+}
--
2.30.1
