diff mbox series

[16/21] libs/guest: make a cpu policy compatible with older Xen versions

Message ID 20210323095849.37858-17-roger.pau@citrix.com (mailing list archive)
State Superseded
Headers show
Series libs/guest: new CPUID/MSR interface | expand

Commit Message

Roger Pau Monne March 23, 2021, 9:58 a.m. UTC
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>
---
 tools/include/xenctrl.h         |  4 ++++
 tools/libs/guest/xg_cpuid_x86.c | 39 ++++++++++++++++++++++++++++-----
 2 files changed, 37 insertions(+), 6 deletions(-)

Comments

Jan Beulich March 31, 2021, 3:29 p.m. UTC | #1
On 23.03.2021 10:58, Roger Pau Monne wrote:
> --- a/tools/libs/guest/xg_cpuid_x86.c
> +++ b/tools/libs/guest/xg_cpuid_x86.c
> @@ -436,6 +436,7 @@ 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 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);
> @@ -504,12 +505,8 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t domid, bool restore,
>       */
>      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);
>      }

The comment ahead of this if() wants moving to ...

> @@ -1230,3 +1227,33 @@ 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;
> +    }
> +
> +    policy->cpuid->basic.rdrand = host->cpuid->basic.rdrand;
> +
> +    if ( hvm )
> +        policy->cpuid->feat.mpx = host->cpuid->feat.mpx;

... or cloning ahead of these two.

Jan
Andrew Cooper April 1, 2021, 4:31 p.m. UTC | #2
On 23/03/2021 09:58, Roger Pau Monne wrote:
> 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>
> ---
>  tools/include/xenctrl.h         |  4 ++++
>  tools/libs/guest/xg_cpuid_x86.c | 39 ++++++++++++++++++++++++++++-----
>  2 files changed, 37 insertions(+), 6 deletions(-)
>
> diff --git a/tools/include/xenctrl.h b/tools/include/xenctrl.h
> index 5f3e5e17e9d..6f7158156fa 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 previous Xen versions. */
> +int xc_cpu_policy_make_compatible(xc_interface *xch, xc_cpu_policy_t policy,
> +                                  bool hvm);

I think this probably wants  "pre-4.14(?)" somewhere obvious, because
"compatible" on its own is very ambiguous.

~Andrew
diff mbox series

Patch

diff --git a/tools/include/xenctrl.h b/tools/include/xenctrl.h
index 5f3e5e17e9d..6f7158156fa 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 previous 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 4afca3249ba..2abaf400a2b 100644
--- a/tools/libs/guest/xg_cpuid_x86.c
+++ b/tools/libs/guest/xg_cpuid_x86.c
@@ -436,6 +436,7 @@  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 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);
@@ -504,12 +505,8 @@  int xc_cpuid_apply_policy(xc_interface *xch, uint32_t domid, bool restore,
      */
     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);
     }
 
     if ( featureset )
@@ -1230,3 +1227,33 @@  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;
+    }
+
+    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;
+}