[Qemu-devel] [PATCH] target-i386: set model=6 on qemu64 & qemu32 CPU models

[Eduardo Habkost <ehabkost@redhat.com>]

There's no Intel CPU with family=6,model=2, and Linux and Windows guests
disable SEP when seeing that combination due to Pentium Pro erratum #82.

In addition to just having SEP ignored by guests, Skype (and maybe other
applications) runs sysenter directly without passing through ntdll on
Windows, and crashes because Windows ignored the SEP CPUID bit.

So, having model > 2 is a better default on qemu64 and qemu32 for two
reasons: making SEP really available for guests, and avoiding crashing
applications that work on bare metal.

model=3 would fix the problem, but it causes CPU enumeration problems
for Windows guests[1]. So this patch sets model=6, that matches "Athlon
(PM core)" on AMD and "P2 with on-die L2 cache" on Intel and it allows
Windows to use all CPUs as well as fixing sysenter.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=508623

Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
 include/hw/i386/pc.h | 8 ++++++++
 target-i386/cpu.c    | 4 ++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 7fb04d8..195e962 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -258,6 +258,14 @@ int e820_add_entry(uint64_t, uint64_t, uint32_t);
             .driver = TYPE_X86_CPU,\
             .property = "pmu",\
             .value = "on",\
+        },{\
+            .driver   = "qemu64-" TYPE_X86_CPU,\
+            .property = "model",\
+            .value    = stringify(2),\
+        },{\
+            .driver   = "qemu32-" TYPE_X86_CPU,\
+            .property = "model",\
+            .value    = stringify(3),\
         }
 
 #define PC_COMPAT_1_4 \
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index c36345e..36cfbce 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -544,7 +544,7 @@ static x86_def_t builtin_x86_defs[] = {
         .level = 4,
         .vendor = CPUID_VENDOR_AMD,
         .family = 6,
-        .model = 2,
+        .model = 6,
         .stepping = 3,
         .features[FEAT_1_EDX] =
             PPRO_FEATURES |
@@ -647,7 +647,7 @@ static x86_def_t builtin_x86_defs[] = {
         .level = 4,
         .vendor = CPUID_VENDOR_INTEL,
         .family = 6,
-        .model = 3,
+        .model = 6,
         .stepping = 3,
         .features[FEAT_1_EDX] =
             PPRO_FEATURES,
-- 
1.8.3.1