[Qemu-devel] [PULL 1/5] target-i386: Set model=6 on qemu64 & qemu32 CPU models

["Andreas Färber" <afaerber@suse.de>]

From: 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 let's set 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>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
---
 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 9b2ddc4..6083839 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -230,6 +230,14 @@ int e820_add_entry(uint64_t, uint64_t, uint32_t);
             .driver   = "e1000",\
             .property = "mitigation",\
             .value    = "off",\
+        },{\
+            .driver   = "qemu64-" TYPE_X86_CPU,\
+            .property = "model",\
+            .value    = stringify(2),\
+        },{\
+            .driver   = "qemu32-" TYPE_X86_CPU,\
+            .property = "model",\
+            .value    = stringify(3),\
         }
 
 #define PC_COMPAT_1_5 \
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index b682802..c1c994f 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -545,7 +545,7 @@ 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 |
@@ -648,7 +648,7 @@ 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,
-- 
1.8.1.4