@@ -754,6 +754,10 @@ int xc_cpu_policy_get_msr(xc_interface *xch, const xc_cpu_policy_t *policy,
bool xc_cpu_policy_is_compatible(xc_interface *xch, xc_cpu_policy_t *host,
xc_cpu_policy_t *guest);
+/* Make a policy compatible with pre-4.13 Xen versions. */
+int xc_cpu_policy_make_compat_4_12(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);
@@ -441,6 +441,7 @@ 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);
@@ -505,21 +506,9 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t domid, bool restore,
if ( restore )
{
- /*
- * Account for feature which have been disabled by default since Xen 4.13,
- * so migrated-in VM's don't risk seeing features disappearing.
- */
- p->basic.rdrand = test_bit(X86_FEATURE_RDRAND, host_featureset);
-
- if ( di.hvm )
- {
- p->feat.mpx = test_bit(X86_FEATURE_MPX, host_featureset);
- }
-
- /* Clamp maximum leaves to the ones supported on 4.12. */
- p->basic.max_leaf = min(p->basic.max_leaf, 0xdu);
- p->feat.max_subleaf = 0;
- p->extd.max_leaf = min(p->extd.max_leaf, 0x1cu);
+ policy.cpuid = *p;
+ xc_cpu_policy_make_compat_4_12(xch, &policy, di.hvm);
+ *p = policy.cpuid;
}
if ( featureset )
@@ -921,3 +910,42 @@ bool xc_cpu_policy_is_compatible(xc_interface *xch, xc_cpu_policy_t *host,
return false;
}
+
+int xc_cpu_policy_make_compat_4_12(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;
+
+ /* Clamp maximum leaves to the ones supported on pre-4.13. */
+ policy->cpuid.basic.max_leaf = min(policy->cpuid.basic.max_leaf, 0xdu);
+ policy->cpuid.feat.max_subleaf = 0;
+ policy->cpuid.extd.max_leaf = min(policy->cpuid.extd.max_leaf, 0x1cu);
+
+ out:
+ xc_cpu_policy_destroy(host);
+ return rc;
+}
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.pau@citrix.com> --- Changes since v3: - Rename function to xc_cpu_policy_make_compat_4_12. Changes since v1: - Move comments and explicitly mention pre-4.13 Xen. --- tools/include/xenguest.h | 4 +++ tools/libs/guest/xg_cpuid_x86.c | 58 ++++++++++++++++++++++++--------- 2 files changed, 47 insertions(+), 15 deletions(-)