[Xen-devel] [PATCH 06/10] x86/cpuid: Handle leaf 0x6 in guest_cpuid()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

The thermal/performance leaf was previously hidden from HVM guests, but fully
visible to PV guests.  Most of the leaf refers to MSR availability, and there
is nothing an unprivileged PV guest can do with the information, so hide the
leaf entirely.

The PV MSR handling logic as minimal support for some thermal/perf operations
from the hardware domain, so leak through the implemented subset of features.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
---
 xen/arch/x86/cpuid.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index 7862d62..2a5e011 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -167,6 +167,7 @@ static void recalculate_misc(struct cpuid_policy *p)
     p->basic.raw[0x4] = p->basic.raw[0x7] = p->basic.raw[0xd] = EMPTY_LEAF;
 
     p->basic.raw[0x5] = EMPTY_LEAF; /* MONITOR not exposed to guests. */
+    p->basic.raw[0x6] = EMPTY_LEAF; /* Therm/Power not exposed to guests. */
 
     p->basic.raw[0x8] = EMPTY_LEAF;
     p->basic.raw[0xc] = EMPTY_LEAF;
@@ -648,8 +649,7 @@ static void pv_cpuid(uint32_t leaf, uint32_t subleaf, 
struct cpuid_leaf *res)
         *res = EMPTY_LEAF;
         break;
 
-    case 0x0 ... 0x5:
-    case 0x7 ... 0x9:
+    case 0x0 ... 0x9:
     case 0xc ... XSTATE_CPUID:
     case 0x80000000 ... 0xffffffff:
         ASSERT_UNREACHABLE();
@@ -683,8 +683,7 @@ static void hvm_cpuid(uint32_t leaf, uint32_t subleaf, 
struct cpuid_leaf *res)
             res->a = (res->a & ~0xff) | 3;
         break;
 
-    case 0x0 ... 0x5:
-    case 0x7 ... 0x9:
+    case 0x0 ... 0x9:
     case 0xc ... XSTATE_CPUID:
     case 0x80000000 ... 0xffffffff:
         ASSERT_UNREACHABLE();
@@ -744,7 +743,7 @@ void guest_cpuid(const struct vcpu *v, uint32_t leaf,
             goto legacy;
 
         case 0x0 ... 0x3:
-        case 0x5:
+        case 0x5 ... 0x6:
         case 0x8 ... 0x9:
         case 0xc:
             *res = p->basic.raw[leaf];
@@ -942,6 +941,22 @@ void guest_cpuid(const struct vcpu *v, uint32_t leaf,
             *res = raw_policy.basic.raw[leaf];
         break;
 
+    case 0x6:
+        /*
+         * Leak the implemented-subset of therm/power features into PV
+         * hardware domain kernels.
+         */
+        if ( is_pv_domain(d) && is_hardware_domain(d) &&
+             guest_kernel_mode(v, guest_cpu_user_regs()) )
+        {
+            /* Temp, Turbo, ARAT. */
+            res->a = raw_policy.basic.raw[leaf].a & 0x00000007;
+
+            /* APERF/MPERF, perf/enery bias. */
+            res->c = raw_policy.basic.raw[leaf].c & 0x00000009;
+        }
+        break;
+
     case 0x7:
         switch ( subleaf )
         {
-- 
2.1.4


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