Re: [Qemu-devel] [PATCH] target-i386: n270 can MOVBE

[Borislav Petkov]

Hi Andreas,

On Fri, Feb 08, 2013 at 12:38:03PM +0100, Andreas Färber wrote:
> Am 08.02.2013 10:30, schrieb Borislav Petkov:
> > From: Borislav Petkov <address@hidden>
> > 
> > The Atom core (cpu name "n270" in QEMU speak) supports MOVBE. This is
> > needed when booting 3.8 and later linux kernels built with the MATOM
> > target because we require MOVBE in order to boot properly now.
> > 
> > Cc: "H. Peter Anvin" <address@hidden>
> > Cc: Richard Henderson <address@hidden>
> > Signed-off-by: Borislav Petkov <address@hidden>
> 
> Please CC me on cpu.c changes (cf. MAINTAINERS).

Wow, qemu has get_maintainer.pl too:

$ git show HEAD | ./scripts/get_maintainer.pl
"Andreas Färber" <address@hidden> (supporter:CPU)
address@hidden (odd fixer:X86

:-)

Ok, fixed.

> >          .ext_features = CPUID_EXT_SSE3 | CPUID_EXT_MONITOR | 
> > CPUID_EXT_SSSE3 |
> > -            CPUID_EXT_DSCPL | CPUID_EXT_EST | CPUID_EXT_TM2 | 
> > CPUID_EXT_XTPR,
> > +            CPUID_EXT_DSCPL | CPUID_EXT_EST | CPUID_EXT_TM2 | 
> > CPUID_EXT_XTPR |
> > +       CPUID_EXT_MOVBE,
> 
> Tab. Please use scripts/checkpatch.pl to verify before sending.

Done.

> >          .ext2_features = (PPRO_FEATURES & CPUID_EXT2_AMD_ALIASES) |
> >              CPUID_EXT2_NX,
> >          .ext3_features = CPUID_EXT3_LAHF_LM,
> 
> Otherwise if someone can ack (or if you can point me to a manual), this
> looks like a good bugfix for v1.4.

Right, I don't know what v1.4 is but this still needs Richard's patchset
enabling MOVBE dynamic translation in qemu to go in first before
enabling MOVBE for the n270 model.

Anyway, fixed patch is below.

> CC'ing some more CPU'ish people.

Well, if you do cat /proc/cpuinfo on an Atom, you can see movbe there.

Here it is from my atom box:

processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 28
model name      : Intel(R) Atom(TM) CPU N270   @ 1.60GHz
stepping        : 2
microcode       : 0x208
cpu MHz         : 800.000
cache size      : 512 KB
physical id     : 0
siblings        : 1
core id         : 0
cpu cores       : 1
apicid          : 0
initial apicid  : 0
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 10
wp              : yes
flags           : fpu vme de tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat 
clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe constant_tsc arch_perfmon pebs 
bts aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 xtpr pdcm movbe lahf_lm 
dtherm
bogomips        : 3192.01
clflush size    : 64
cache_alignment : 64
address sizes   : 32 bits physical, 32 bits virtual
power management:

Or, more cpu vendor-y, do CPUID.EAX(1) on an n270 and bit 22 in ECX is
set. Here is a full base cpuid leafs dump:

$ ./dump_cpuid
max base function: 0x0000000a
CPUID.EAX=0x00000000
EAX=0x0000000a, EBX=0x756e6547, ECX=0x6c65746e, EDX=0x49656e69
CPUID.EAX=0x00000001
EAX=0x000106c2, EBX=0x01020800, ECX=0x0040c39d, EDX=0xbfe9fbff
                                    ^^^^^
                                    bit 22 here is MOVBE presence.

CPUID.EAX=0x00000002
EAX=0x4fba5901, EBX=0x0e3080c0, ECX=0x00000000, EDX=0x00000000
CPUID.EAX=0x00000003
EAX=0x00000000, EBX=0x00000000, ECX=0x00000000, EDX=0x00000000
CPUID.EAX=0x00000004
EAX=0x00004121, EBX=0x0140003f, ECX=0x0000003f, EDX=0x00000001
CPUID.EAX=0x00000005
EAX=0x00000040, EBX=0x00000040, ECX=0x00000003, EDX=0x00020220
CPUID.EAX=0x00000006
EAX=0x00000001, EBX=0x00000002, ECX=0x00000001, EDX=0x00000000
CPUID.EAX=0x00000007
EAX=0x00000000, EBX=0x00000000, ECX=0x00000000, EDX=0x00000000
CPUID.EAX=0x00000008
EAX=0x00000000, EBX=0x00000000, ECX=0x00000000, EDX=0x00000000
CPUID.EAX=0x00000009
EAX=0x00000000, EBX=0x00000000, ECX=0x00000000, EDX=0x00000000
CPUID.EAX=0x0000000a
EAX=0x07280203, EBX=0x00000000, ECX=0x00000000, EDX=0x00002501

And the official document is this one here:

http://www.intel.com/content/www/us/en/processors/processor-identification-cpuid-instruction-note.html

Table 5-5 Feature Flags Reported in the ECX Register (Sheet 1 of 2).

HTH.

--
>From 5371732b65fbb9a873b52c67a260ffcaf7caf88d Mon Sep 17 00:00:00 2001
From: Borislav Petkov <address@hidden>
Date: Fri, 8 Feb 2013 10:19:44 +0100
Subject: [PATCH] target-i386: n270 can MOVBE
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The Atom core (cpu name "n270" in QEMU speak) supports MOVBE. This is
needed when booting 3.8 and later linux kernels built with the MATOM
target because we require MOVBE in order to boot properly now.

Cc: "H. Peter Anvin" <address@hidden>
Cc: Richard Henderson <address@hidden>
Cc: "Andreas Färber" <address@hidden>
Signed-off-by: Borislav Petkov <address@hidden>
---
 target-i386/cpu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index 4a516e1f9e25..36a133462a8d 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -620,7 +620,8 @@ static x86_def_t builtin_x86_defs[] = {
             CPUID_ACPI | CPUID_SS | CPUID_HT | CPUID_TM | CPUID_PBE,
             /* Some CPUs got no CPUID_SEP */
         .ext_features = CPUID_EXT_SSE3 | CPUID_EXT_MONITOR | CPUID_EXT_SSSE3 |
-            CPUID_EXT_DSCPL | CPUID_EXT_EST | CPUID_EXT_TM2 | CPUID_EXT_XTPR,
+            CPUID_EXT_DSCPL | CPUID_EXT_EST | CPUID_EXT_TM2 | CPUID_EXT_XTPR |
+            CPUID_EXT_MOVBE,
         .ext2_features = (PPRO_FEATURES & CPUID_EXT2_AMD_ALIASES) |
             CPUID_EXT2_NX,
         .ext3_features = CPUID_EXT3_LAHF_LM,
-- 
1.8.1.2.422.g08c0e7f

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
--