[Xen-changelog] [xen master] x86/cpuid: Handle leaf 0xb in guest_cpuid()

[patchbot@xxxxxxx]

commit 5853cd94d981fe83adb3173fa759284a06733dd4
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Fri Feb 17 18:31:45 2017 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Mon Mar 13 13:44:40 2017 +0000

    x86/cpuid: Handle leaf 0xb in guest_cpuid()
    
    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.
    
    In practice, leaf 0xb is tightly linked with x2APIC, and x2APIC is offered 
to
    guests on AMD hardware, as Xen's APIC emulation is x2APIC capable even if
    hardware isn't.
    
    Sensibly exposing the rest of the leaf requires further topology
    infrastructure.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/cpuid.c | 36 +++++++++++++++++++++---------------
 1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index b57618e..f80de93 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -171,6 +171,7 @@ static void recalculate_misc(struct cpuid_policy *p)
     p->basic.raw[0x6] = EMPTY_LEAF; /* Therm/Power not exposed to guests. */
 
     p->basic.raw[0x8] = EMPTY_LEAF;
+    p->basic.raw[0xb] = EMPTY_LEAF; /* TODO: Rework topology logic. */
     p->basic.raw[0xc] = EMPTY_LEAF;
 
     p->extd.e1d &= ~CPUID_COMMON_1D_FEATURES;
@@ -636,12 +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(). */
@@ -657,13 +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(). */
@@ -723,8 +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;
         }
@@ -945,6 +934,23 @@ void guest_cpuid(const struct vcpu *v, uint32_t leaf,
         }
         break;
 
+    case 0xb:
+        /*
+         * In principle, this leaf is Intel-only.  In practice, it is tightly
+         * coupled with x2apic, and we offer an x2apic-capable APIC emulation
+         * to guests on AMD hardware as well.
+         *
+         * TODO: Rework topology logic.
+         */
+        if ( p->basic.x2apic )
+        {
+            *(uint8_t *)&res->c = subleaf;
+
+            /* Fix the x2APIC identifier. */
+            res->d = v->vcpu_id * 2;
+        }
+        break;
+
     case XSTATE_CPUID:
         switch ( subleaf )
         {
--
generated by git-patchbot for /home/xen/git/xen.git#master

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