x86/cpuid: Handle leaf 0x5 in guest_cpuid()

The MONITOR flag isn't exposed to guests.  The existing toolstack logic, and
pv_cpuid() in the hypervisor, zero the MONITOR leaf for queries.

However, the MONITOR leaf is still visible in the hardware domains native
CPUID view, and Linux depends on this to set up C-state information.  Leak the
hosts MONITOR leaf under the same circumstances that the MONITOR feature is
leaked.

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

diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index d77065fdab5579a439e5be894fb35dfb4b428d4e..78c786b4bc4a848c65837094ecae71c41e222500 100644 (file)
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -167,6 +167,8 @@ static void recalculate_misc(struct cpuid_policy *p)
     p->basic.raw_fms &= 0x0fff0fff; /* Clobber Processor Type on Intel. */
     p->basic.apic_id = 0; /* Dynamic. */
 
+    p->basic.raw[0x5] = EMPTY_LEAF; /* MONITOR not exposed to guests. */
+
     p->basic.raw[0x8] = EMPTY_LEAF;
     p->basic.raw[0xc] = EMPTY_LEAF;
 
@@ -643,13 +645,12 @@ static void pv_cpuid(uint32_t leaf, uint32_t subleaf, struct cpuid_leaf *res)
             res->a = (res->a & ~0xff) | 3;
         break;
 
-    case 0x00000005: /* MONITOR/MWAIT */
     case 0x0000000b: /* Extended Topology Enumeration */
     unsupported:
         *res = EMPTY_LEAF;
         break;
 
-    case 0x0 ... 0x4:
+    case 0x0 ... 0x5:
     case 0x7 ... 0x9:
     case 0xc ... XSTATE_CPUID:
     case 0x80000000 ... 0xffffffff:
@@ -684,7 +685,7 @@ static void hvm_cpuid(uint32_t leaf, uint32_t subleaf, struct cpuid_leaf *res)
             res->a = (res->a & ~0xff) | 3;
         break;
 
-    case 0x0 ... 0x4:
+    case 0x0 ... 0x5:
     case 0x7 ... 0x9:
     case 0xc ... XSTATE_CPUID:
     case 0x80000000 ... 0xffffffff:
@@ -745,6 +746,7 @@ void guest_cpuid(const struct vcpu *v, uint32_t leaf,
             goto legacy;
 
         case 0x0 ... 0x3:
+        case 0x5:
         case 0x8 ... 0x9:
         case 0xc:
             *res = p->basic.raw[leaf];
@@ -929,6 +931,18 @@ void guest_cpuid(const struct vcpu *v, uint32_t leaf,
         }
         goto common_leaf1_adjustments;
 
+    case 0x5:
+        /*
+         * Leak the hardware MONITOR leaf under the same conditions that the
+         * MONITOR feature flag is leaked.  See above for details.
+         */
+        regs = guest_cpu_user_regs();
+        if ( is_pv_domain(d) && is_hardware_domain(d) &&
+             guest_kernel_mode(v, regs) && cpu_has_monitor &&
+             regs->entry_vector == TRAP_gp_fault )
+            *res = raw_policy.basic.raw[leaf];
+        break;
+
     case 0x7:
         switch ( subleaf )
         {