[PATCH v2 04/21] libs/guest: introduce helper to fetch a system cpu policy

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

Such helper is based on the existing functions to fetch a CPUID and
MSR policies, but uses the xc_cpu_policy_t type to return the data to
the caller.

Note some helper functions are introduced, those are split from
xc_cpu_policy_get_system because they will be used by other functions
also.

No user of the interface introduced on the patch.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Changes since v1:
 - Always return -1 on error from xc_cpu_policy_get_system.
 - Only print detailed error messages if err_leaf or err_msr is != -1.
 - Rename idx function parameter to policy_idx.
---
 tools/include/xenctrl.h         |  4 +++
 tools/libs/guest/xg_cpuid_x86.c | 54 +++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/tools/include/xenctrl.h b/tools/include/xenctrl.h
index 1aba814f01c..187df5c5d2d 100644
--- a/tools/include/xenctrl.h
+++ b/tools/include/xenctrl.h
@@ -2596,6 +2596,10 @@ typedef struct xc_cpu_policy *xc_cpu_policy_t;
 xc_cpu_policy_t xc_cpu_policy_init(void);
 void xc_cpu_policy_destroy(xc_cpu_policy_t policy);
 
+/* Retrieve a system policy, or get/set a domains policy. */
+int xc_cpu_policy_get_system(xc_interface *xch, unsigned int policy_idx,
+                             xc_cpu_policy_t policy);
+
 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 8e3a1a8cbf2..78fbc7db9d3 100644
--- a/tools/libs/guest/xg_cpuid_x86.c
+++ b/tools/libs/guest/xg_cpuid_x86.c
@@ -678,3 +678,57 @@ void xc_cpu_policy_destroy(xc_cpu_policy_t policy)
     if ( policy )
         free(policy);
 }
+
+static int deserialize_policy(xc_interface *xch, xc_cpu_policy_t policy,
+                              unsigned int nr_leaves, unsigned int nr_entries)
+{
+    uint32_t err_leaf = -1, err_subleaf = -1, err_msr = -1;
+    int rc;
+
+    rc = x86_cpuid_copy_from_buffer(&policy->cpuid, policy->leaves,
+                                    nr_leaves, &err_leaf, &err_subleaf);
+    if ( rc )
+    {
+        if ( err_leaf != -1 )
+            ERROR("Failed to deserialise CPUID (err leaf %#x, subleaf %#x) (%d 
= %s)",
+                  err_leaf, err_subleaf, -rc, strerror(-rc));
+        return rc;
+    }
+
+    rc = x86_msr_copy_from_buffer(&policy->msr, policy->entries,
+                                  nr_entries, &err_msr);
+    if ( rc )
+    {
+        if ( err_msr != -1 )
+            ERROR("Failed to deserialise MSR (err MSR %#x) (%d = %s)",
+                  err_msr, -rc, strerror(-rc));
+        return rc;
+    }
+
+    return 0;
+}
+
+int xc_cpu_policy_get_system(xc_interface *xch, unsigned int policy_idx,
+                             xc_cpu_policy_t policy)
+{
+    unsigned int nr_leaves = ARRAY_SIZE(policy->leaves);
+    unsigned int nr_entries = ARRAY_SIZE(policy->entries);
+    int rc;
+
+    rc = xc_get_system_cpu_policy(xch, policy_idx, &nr_leaves, policy->leaves,
+                                  &nr_entries, policy->entries);
+    if ( rc )
+    {
+        PERROR("Failed to obtain %u policy", policy_idx);
+        return rc;
+    }
+
+    rc = deserialize_policy(xch, policy, nr_leaves, nr_entries);
+    if ( rc )
+    {
+        errno = -rc;
+        rc = -1;
+    }
+
+    return rc;
+}
-- 
2.30.1