pc: Use "min-[x]level" on compat_props

Since the automatic cpuid-level code was introduced in commit
c39c0edf9b ("target-i386: Automatically
set level/xlevel/xlevel2 when needed"), the CPU model tables just define
the default CPUID level code (set using "min-level").  Setting
"[x]level" forces CPUID level to a specific value and disable the
automatic-level logic.

But the PC compat code was not updated and the existing "[x]level"
compat properties broke compatibility for people using features that
triggered the auto-level code.  To keep previous behavior, we should set
"min-[x]level" instead of "[x]level" on compat_props.

This was not a problem for most cases, because old machine-types don't
have full-cpuid-auto-level enabled.  The only common use case it broke
was the CPUID[7] auto-level code, that was already enabled since the
first CPUID[7] feature was introduced (in QEMU 1.4.0).

This causes the regression reported at:
https://bugzilla.redhat.com/show_bug.cgi?id=1454641

Change the PC compat code to use "min-[x]level" instead of "[x]level" on
compat_props, and add new test cases to ensure we don't break this
again.

Reported-by: "Guo, Zhiyi" <zhguo@redhat.com>
Fixes: c39c0edf9b ("target-i386: Automatically set level/xlevel/xlevel2 when needed")
Cc: qemu-stable@nongnu.org
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

include/hw/i386/pc.h

@@ -566,75 +566,75 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
         .value    = "off",\
     },{\
         .driver   = "qemu64" "-" TYPE_X86_CPU,\
-        .property = "level",\
+        .property = "min-level",\
         .value    = stringify(4),\
     },{\
         .driver   = "kvm64" "-" TYPE_X86_CPU,\
-        .property = "level",\
+        .property = "min-level",\
         .value    = stringify(5),\
     },{\
         .driver   = "pentium3" "-" TYPE_X86_CPU,\
-        .property = "level",\
+        .property = "min-level",\
         .value    = stringify(2),\
     },{\
         .driver   = "n270" "-" TYPE_X86_CPU,\
-        .property = "level",\
+        .property = "min-level",\
         .value    = stringify(5),\
     },{\
         .driver   = "Conroe" "-" TYPE_X86_CPU,\
-        .property = "level",\
+        .property = "min-level",\
         .value    = stringify(4),\
     },{\
         .driver   = "Penryn" "-" TYPE_X86_CPU,\
-        .property = "level",\
+        .property = "min-level",\
         .value    = stringify(4),\
     },{\
         .driver   = "Nehalem" "-" TYPE_X86_CPU,\
-        .property = "level",\
+        .property = "min-level",\
         .value    = stringify(4),\
     },{\
         .driver   = "n270" "-" TYPE_X86_CPU,\
-        .property = "xlevel",\
+        .property = "min-xlevel",\
         .value    = stringify(0x8000000a),\
     },{\
         .driver   = "Penryn" "-" TYPE_X86_CPU,\
-        .property = "xlevel",\
+        .property = "min-xlevel",\
         .value    = stringify(0x8000000a),\
     },{\
         .driver   = "Conroe" "-" TYPE_X86_CPU,\
-        .property = "xlevel",\
+        .property = "min-xlevel",\
         .value    = stringify(0x8000000a),\
     },{\
         .driver   = "Nehalem" "-" TYPE_X86_CPU,\
-        .property = "xlevel",\
+        .property = "min-xlevel",\
         .value    = stringify(0x8000000a),\
     },{\
         .driver   = "Westmere" "-" TYPE_X86_CPU,\
-        .property = "xlevel",\
+        .property = "min-xlevel",\
         .value    = stringify(0x8000000a),\
     },{\
         .driver   = "SandyBridge" "-" TYPE_X86_CPU,\
-        .property = "xlevel",\
+        .property = "min-xlevel",\
         .value    = stringify(0x8000000a),\
     },{\
         .driver   = "IvyBridge" "-" TYPE_X86_CPU,\
-        .property = "xlevel",\
+        .property = "min-xlevel",\
         .value    = stringify(0x8000000a),\
     },{\
         .driver   = "Haswell" "-" TYPE_X86_CPU,\
-        .property = "xlevel",\
+        .property = "min-xlevel",\
         .value    = stringify(0x8000000a),\
     },{\
         .driver   = "Haswell-noTSX" "-" TYPE_X86_CPU,\
-        .property = "xlevel",\
+        .property = "min-xlevel",\
         .value    = stringify(0x8000000a),\
     },{\
         .driver   = "Broadwell" "-" TYPE_X86_CPU,\
-        .property = "xlevel",\
+        .property = "min-xlevel",\
         .value    = stringify(0x8000000a),\
     },{\
         .driver   = "Broadwell-noTSX" "-" TYPE_X86_CPU,\
-        .property = "xlevel",\
+        .property = "min-xlevel",\
         .value    = stringify(0x8000000a),\
     },{\
         .driver = TYPE_X86_CPU,\
@@ -860,7 +860,7 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
         .value    = stringify(2),\
     },{\
         .driver   = "Conroe-" TYPE_X86_CPU,\
-        .property = "level",\
+        .property = "min-level",\
         .value    = stringify(2),\
     },{\
         .driver   = "Penryn-" TYPE_X86_CPU,\
@@ -868,7 +868,7 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
         .value    = stringify(2),\
     },{\
         .driver   = "Penryn-" TYPE_X86_CPU,\
-        .property = "level",\
+        .property = "min-level",\
         .value    = stringify(2),\
     },{\
         .driver   = "Nehalem-" TYPE_X86_CPU,\
@@ -876,7 +876,7 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
         .value    = stringify(2),\
     },{\
         .driver   = "Nehalem-" TYPE_X86_CPU,\
-        .property = "level",\
+        .property = "min-level",\
         .value    = stringify(2),\
     },{\
         .driver   = "virtio-net-pci",\

tests/test-x86-cpuid-compat.c

@@ -313,6 +313,44 @@ int main(int argc, char **argv)
     add_cpuid_test("x86/cpuid/auto-xlevel2/pc-2.7",
                    "-machine pc-i440fx-2.7 -cpu 486,+xstore",
                    "xlevel2", 0);
+    /*
+     * QEMU 1.4.0 had auto-level enabled for CPUID[7], already,
+     * and the compat code that sets default level shouldn't
+     * disable the auto-level=7 code:
+     */
+    add_cpuid_test("x86/cpuid/auto-level7/pc-i440fx-1.4/off",
+                   "-machine pc-i440fx-1.4 -cpu Nehalem",
+                   "level", 2);
+    add_cpuid_test("x86/cpuid/auto-level7/pc-i440fx-1.5/on",
+                   "-machine pc-i440fx-1.4 -cpu Nehalem,+smap",
+                   "level", 7);
+    add_cpuid_test("x86/cpuid/auto-level7/pc-i440fx-2.3/off",
+                   "-machine pc-i440fx-2.3 -cpu Penryn",
+                   "level", 4);
+    add_cpuid_test("x86/cpuid/auto-level7/pc-i440fx-2.3/on",
+                   "-machine pc-i440fx-2.3 -cpu Penryn,+erms",
+                   "level", 7);
+    add_cpuid_test("x86/cpuid/auto-level7/pc-i440fx-2.9/off",
+                   "-machine pc-i440fx-2.9 -cpu Conroe",
+                   "level", 10);
+    add_cpuid_test("x86/cpuid/auto-level7/pc-i440fx-2.9/on",
+                   "-machine pc-i440fx-2.9 -cpu Conroe,+erms",
+                   "level", 10);
+
+    /*
+     * xlevel doesn't have any feature that triggers auto-level
+     * code on old machine-types.  Just check that the compat code
+     * is working correctly:
+     */
+    add_cpuid_test("x86/cpuid/xlevel-compat/pc-i440fx-2.3",
+                   "-machine pc-i440fx-2.3 -cpu SandyBridge",
+                   "xlevel", 0x8000000a);
+    add_cpuid_test("x86/cpuid/xlevel-compat/pc-i440fx-2.4/npt-off",
+                   "-machine pc-i440fx-2.4 -cpu SandyBridge,",
+                   "xlevel", 0x80000008);
+    add_cpuid_test("x86/cpuid/xlevel-compat/pc-i440fx-2.4/npt-on",
+                   "-machine pc-i440fx-2.4 -cpu SandyBridge,+npt",
+                   "xlevel", 0x80000008);
 
     /* Test feature parsing */
     add_feature_test("x86/cpuid/features/plus",