x86/msr: Expose MSR_ARCH_CAPS in the raw and host policies

MSR_ARCH_CAPS is still not supported for guests yet (other than the hardware
domain), until the toolstack learns how to construct an MSR policy.

However, we want access to the host ARCH_CAPS_TSX_CTRL value in particular for
testing purposes.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/msr.c

@@ -47,8 +47,13 @@ struct msr_policy __read_mostly hvm_def_msr_policy;
 
 static void __init calculate_raw_policy(void)
 {
+    struct msr_policy *mp = &raw_msr_policy;
+
     /* 0x000000ce  MSR_INTEL_PLATFORM_INFO */
     /* Was already added by probe_cpuid_faulting() */
+
+    if ( cpu_has_arch_caps )
+        rdmsrl(MSR_ARCH_CAPABILITIES, mp->arch_caps.raw);
 }
 
 static void __init calculate_host_policy(void)
@@ -60,6 +65,12 @@ static void __init calculate_host_policy(void)
     /* 0x000000ce  MSR_INTEL_PLATFORM_INFO */
     /* probe_cpuid_faulting() sanity checks presence of MISC_FEATURES_ENABLES */
     mp->platform_info.cpuid_faulting = cpu_has_cpuid_faulting;
+
+    /* Temporary, until we have known_features[] for feature bits in MSRs. */
+    mp->arch_caps.raw &=
+        (ARCH_CAPS_RDCL_NO | ARCH_CAPS_IBRS_ALL | ARCH_CAPS_RSBA |
+         ARCH_CAPS_SKIP_L1DFL | ARCH_CAPS_SSB_NO | ARCH_CAPS_MDS_NO |
+         ARCH_CAPS_IF_PSCHANGE_MC_NO | ARCH_CAPS_TSX_CTRL | ARCH_CAPS_TAA_NO);
 }
 
 static void __init calculate_pv_max_policy(void)
@@ -67,6 +78,8 @@ static void __init calculate_pv_max_policy(void)
     struct msr_policy *mp = &pv_max_msr_policy;
 
     *mp = host_msr_policy;
+
+    mp->arch_caps.raw = 0; /* Not supported yet. */
 }
 
 static void __init calculate_pv_def_policy(void)
@@ -84,6 +97,8 @@ static void __init calculate_hvm_max_policy(void)
 
     /* It's always possible to emulate CPUID faulting for HVM guests */
     mp->platform_info.cpuid_faulting = true;
+
+    mp->arch_caps.raw = 0; /* Not supported yet. */
 }
 
 static void __init calculate_hvm_def_policy(void)