[Xen-devel] [PATCH 08/10] x86/cpuid: Handle leaf 0xb in guest_cpuid()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Leaf 0xb is reserved by AMD, and uniformly hidden from guests by the toolstack
logic and hypervisor PV logic.

The previous dynamic logic filled in the x2APIC ID for all HVM guests.  This
is modified to respect the entire leaf being reserved by AMD, but is altered
to include PV Intel guests, so they get more sensible values in their emulated
and faulted view of CPUID.

Sensibly exposing the rest of the leaf requires further topology
infrastructure.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
---
 xen/arch/x86/cpuid.c | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index c8dadab..f1bcd7d 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -189,6 +189,9 @@ static void recalculate_misc(struct cpuid_policy *p)
         p->basic.raw[0x3] = EMPTY_LEAF; /* PSN - always hidden. */
         p->basic.raw[0x9] = EMPTY_LEAF; /* DCA - always hidden. */
 
+        /* TODO: Rework topology logic. */
+        p->basic.raw[0xb] = EMPTY_LEAF;
+
         p->extd.vendor_ebx = 0;
         p->extd.vendor_ecx = 0;
         p->extd.vendor_edx = 0;
@@ -208,7 +211,7 @@ static void recalculate_misc(struct cpuid_policy *p)
 
         zero_leaves(p->basic.raw, 0x2, 0x3);
         memset(p->cache.raw, 0, sizeof(p->cache.raw));
-        zero_leaves(p->basic.raw, 0x9, 0xa);
+        zero_leaves(p->basic.raw, 0x9, 0xb);
 
         p->extd.vendor_ebx = p->basic.vendor_ebx;
         p->extd.vendor_ecx = p->basic.vendor_ecx;
@@ -634,12 +637,7 @@ static void pv_cpuid(uint32_t leaf, uint32_t subleaf, 
struct cpuid_leaf *res)
 
     switch ( leaf )
     {
-    case 0x0000000b: /* Extended Topology Enumeration */
-        *res = EMPTY_LEAF;
-        break;
-
-    case 0x0 ... 0xa:
-    case 0xc ... XSTATE_CPUID:
+    case 0x0 ... XSTATE_CPUID:
     case 0x80000000 ... 0xffffffff:
         ASSERT_UNREACHABLE();
         /* Now handled in guest_cpuid(). */
@@ -655,13 +653,7 @@ static void hvm_cpuid(uint32_t leaf, uint32_t subleaf, 
struct cpuid_leaf *res)
 
     switch ( leaf )
     {
-    case 0xb:
-        /* Fix the x2APIC identifier. */
-        res->d = v->vcpu_id * 2;
-        break;
-
-    case 0x0 ... 0xa:
-    case 0xc ... XSTATE_CPUID:
+    case 0x0 ... XSTATE_CPUID:
     case 0x80000000 ... 0xffffffff:
         ASSERT_UNREACHABLE();
         /* Now handled in guest_cpuid(). */
@@ -721,8 +713,7 @@ void guest_cpuid(const struct vcpu *v, uint32_t leaf,
 
         case 0x0 ... 0x3:
         case 0x5 ... 0x6:
-        case 0x8 ... 0xa:
-        case 0xc:
+        case 0x8 ... 0xc:
             *res = p->basic.raw[leaf];
             break;
         }
@@ -959,6 +950,14 @@ void guest_cpuid(const struct vcpu *v, uint32_t leaf,
         }
         break;
 
+    case 0xb:
+        if ( p->x86_vendor == X86_VENDOR_INTEL )
+        {
+            /* Fix the x2APIC identifier. */
+            res->d = v->vcpu_id * 2;
+        }
+        break;
+
     case XSTATE_CPUID:
         switch ( subleaf )
         {
-- 
2.1.4


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