[PATCH 08/13] libs/guest: introduce support for setting guest MSRs

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

Like it's done with CPUID, introduce support for passing MSR values to
xc_cpuid_apply_policy().  The chosen format for expressing MSR policy
data matches the current one used for CPUID.  Note that existing
callers of xc_cpuid_apply_policy() can pass NULL as the value for the
newly introduced 'msr' parameter in order to preserve the same
functionality, and in fact that's done in libxl on this patch.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 tools/include/xenctrl.h         | 21 ++++++++-
 tools/include/xenguest.h        |  5 ++-
 tools/libs/guest/xg_cpuid_x86.c | 76 ++++++++++++++++++++++++++++++++-
 tools/libs/light/libxl_cpuid.c  |  2 +-
 4 files changed, 99 insertions(+), 5 deletions(-)

diff --git a/tools/include/xenctrl.h b/tools/include/xenctrl.h
index 45f05a2d3d7e..786061282c91 100644
--- a/tools/include/xenctrl.h
+++ b/tools/include/xenctrl.h
@@ -1822,6 +1822,21 @@ struct xc_xend_cpuid {
     char *policy[4];
 };
 
+/*
+ * MSR policy data.
+ *
+ * The format of the policy string is the following:
+ *   '1' -> force to 1
+ *   '0' -> force to 0
+ *   'x' -> we don't care (use default)
+ *   'k' -> pass through host value
+ */
+struct xc_msr {
+    uint32_t index;
+    char policy[65];
+};
+#define XC_MSR_INPUT_UNUSED 0xffffffffu
+
 /*
  * Make adjustments to the CPUID settings for a domain.
  *
@@ -1833,13 +1848,15 @@ struct xc_xend_cpuid {
  * Either pass a full new @featureset (and @nr_features), or adjust individual
  * features (@pae, @itsc, @nested_virt).
  *
- * Then (optionally) apply legacy XEND overrides (@xend) to the result.
+ * Then (optionally) apply legacy XEND CPUID overrides (@cpuid) or MSR (@msr)
+ * to the result.
  */
 int xc_cpuid_apply_policy(xc_interface *xch,
                           uint32_t domid, bool restore,
                           const uint32_t *featureset,
                           unsigned int nr_features, bool pae, bool itsc,
-                          bool nested_virt, const struct xc_xend_cpuid *cpuid);
+                          bool nested_virt, const struct xc_xend_cpuid *cpuid,
+                          const struct xc_msr *msr);
 int xc_mca_op(xc_interface *xch, struct xen_mc *mc);
 int xc_mca_op_inject_v2(xc_interface *xch, unsigned int flags,
                         xc_cpumap_t cpumap, unsigned int nr_cpus);
diff --git a/tools/include/xenguest.h b/tools/include/xenguest.h
index 705a93a058fb..be61ff0af7fe 100644
--- a/tools/include/xenguest.h
+++ b/tools/include/xenguest.h
@@ -817,10 +817,13 @@ 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);
 
-/* Apply an array of xc_xend_cpuid leafs to the policy. */
+/* Apply an array of xc_xend_cpuid leafs or xc_msrs to the policy. */
 int xc_cpu_policy_apply_cpuid(xc_interface *xch, xc_cpu_policy_t *policy,
                               const struct xc_xend_cpuid *cpuid,
                               const xc_cpu_policy_t *host);
+int xc_cpu_policy_apply_msr(xc_interface *xch, xc_cpu_policy_t *policy,
+                            const struct xc_msr *msr,
+                            const xc_cpu_policy_t *host);
 
 int xc_get_cpu_levelling_caps(xc_interface *xch, uint32_t *caps);
 int xc_get_cpu_featureset(xc_interface *xch, uint32_t index,
diff --git a/tools/libs/guest/xg_cpuid_x86.c b/tools/libs/guest/xg_cpuid_x86.c
index 0d0970d4bd69..09a012960a43 100644
--- a/tools/libs/guest/xg_cpuid_x86.c
+++ b/tools/libs/guest/xg_cpuid_x86.c
@@ -331,10 +331,74 @@ int xc_cpu_policy_apply_cpuid(xc_interface *xch, 
xc_cpu_policy_t *policy,
     return 0;
 }
 
+int xc_cpu_policy_apply_msr(xc_interface *xch, xc_cpu_policy_t *policy,
+                            const struct xc_msr *msr,
+                            const xc_cpu_policy_t *host)
+{
+    for ( ; msr->index != XC_MSR_INPUT_UNUSED; ++msr )
+    {
+        xen_msr_entry_t cur_msr, host_msr;
+        int rc;
+
+        rc = xc_cpu_policy_get_msr(xch, policy, msr->index, &cur_msr);
+        if ( rc )
+        {
+            ERROR("Failed to get current MSR %#x", msr->index);
+            return rc;
+        }
+        rc = xc_cpu_policy_get_msr(xch, host, msr->index, &host_msr);
+        if ( rc )
+        {
+            ERROR("Failed to get host policy MSR %#x", msr->index);
+            return rc;
+        }
+
+        for ( unsigned int i = 0; i < ARRAY_SIZE(msr->policy) - 1; i++ )
+        {
+            bool val;
+
+            switch ( msr->policy[i] )
+            {
+            case '1':
+                val = true;
+                break;
+
+            case '0':
+                val = false;
+                break;
+
+            case 'x':
+                /* Leave alone: the current policy is the default one. */
+                continue;
+
+            case 'k':
+                val = test_bit(63 - i, &host_msr.val);
+                break;
+
+            default:
+                ERROR("Bad character '%c' in policy string '%s'",
+                      msr->policy[i], msr->policy);
+                return -EINVAL;
+            }
+
+            clear_bit(63 - i, &cur_msr.val);
+            if ( val )
+                set_bit(63 - i, &cur_msr.val);
+        }
+
+        rc = xc_cpu_policy_update_msrs(xch, policy, &cur_msr, 1);
+        if ( rc )
+            return rc;
+    }
+
+    return 0;
+}
+
 int xc_cpuid_apply_policy(xc_interface *xch, uint32_t domid, bool restore,
                           const uint32_t *featureset, unsigned int nr_features,
                           bool pae, bool itsc, bool nested_virt,
-                          const struct xc_xend_cpuid *cpuid)
+                          const struct xc_xend_cpuid *cpuid,
+                          const struct xc_msr *msr)
 {
     int rc;
     bool hvm;
@@ -535,6 +599,16 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t 
domid, bool restore,
         }
     }
 
+    if ( msr )
+    {
+        rc = xc_cpu_policy_apply_msr(xch, policy, msr, host);
+        if ( rc )
+        {
+            rc = -errno;
+            goto out;
+        }
+    }
+
     rc = xc_cpu_policy_set_domain(xch, domid, policy);
     if ( rc )
     {
diff --git a/tools/libs/light/libxl_cpuid.c b/tools/libs/light/libxl_cpuid.c
index f5ce9f97959c..c96aeb3bce46 100644
--- a/tools/libs/light/libxl_cpuid.c
+++ b/tools/libs/light/libxl_cpuid.c
@@ -502,7 +502,7 @@ int libxl__cpuid_legacy(libxl_ctx *ctx, uint32_t domid, 
bool restore,
             info->tsc_mode == LIBXL_TSC_MODE_ALWAYS_EMULATE);
 
     r = xc_cpuid_apply_policy(ctx->xch, domid, restore, NULL, 0,
-                              pae, itsc, nested_virt, info->cpuid);
+                              pae, itsc, nested_virt, info->cpuid, NULL);
     if (r)
         LOGEVD(ERROR, -r, domid, "Failed to apply CPUID policy");
 
-- 
2.40.0