[Qemu-devel] [PULL 09/12] i386: Allow TOPOEXT to be enabled on older kernels

[Eduardo Habkost <ehabkost@redhat.com>]

From: Babu Moger <babu.moger@amd.com>

Enabling TOPOEXT feature might cause compatibility issues if
older kernels does not set this feature. Lets set this feature
unconditionally.

Signed-off-by: Babu Moger <babu.moger@amd.com>
Message-Id: <1528939107-17193-2-git-send-email-babu.moger@amd.com>
[ehabkost: rewrite comment and commit message]
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
 target/i386/kvm.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index 445e0e0b11..2d174f3a91 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -372,6 +372,13 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,
         if (host_tsx_blacklisted()) {
             ret &= ~(CPUID_7_0_EBX_RTM | CPUID_7_0_EBX_HLE);
         }
+    } else if (function == 0x80000001 && reg == R_ECX) {
+        /*
+         * It's safe to enable TOPOEXT even if it's not returned by
+         * GET_SUPPORTED_CPUID.  Unconditionally enabling TOPOEXT here allows
+         * us to keep CPU models including TOPOEXT runnable on older kernels.
+         */
+        ret |= CPUID_EXT3_TOPOEXT;
     } else if (function == 0x80000001 && reg == R_EDX) {
         /* On Intel, kvm returns cpuid according to the Intel spec,
          * so add missing bits according to the AMD spec:
-- 
2.18.0.rc1.1.g3f1ff2140