[PATCH 0/2] KVM: x86 emulator: emulate MOVAPS and MOVAPD SSE instructions

[PATCH 0/2] KVM: x86 emulator: emulate MOVAPS and MOVAPD SSE instructions

[Igor Mammedov]

MS HCK test fails on 32-bit Windows 8.1 due to missing MOVAPS
instruction emulation, this series adds it and while at it,
it adds emulation of MOVAPD which is trivial to implement on
top of MOVAPS.

Igor Mammedov (2):
  KVM: x86 emulator: emulate MOVAPS
  KVM: x86 emulator: emulate MOVAPD

 arch/x86/kvm/emulate.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

-- 
1.8.5.3

[PATCH 1/2] KVM: x86 emulator: emulate MOVAPS

[Igor Mammedov]

HCK memory driver test fails when testing 32-bit Windows 8.1
with baloon driver.

tracing KVM shows error:
reason EXIT_ERR rip 0x81c18326 info 0 0

x/10i 0x81c18326-20
0x0000000081c18312:  add    %al,(%eax)
0x0000000081c18314:  add    %cl,-0x7127711d(%esi)
0x0000000081c1831a:  rolb   $0x0,0x80ec(%ecx)
0x0000000081c18321:  and    $0xfffffff0,%esp
0x0000000081c18324:  mov    %esp,%esi
0x0000000081c18326:  movaps %xmm0,(%esi)
0x0000000081c18329:  movaps %xmm1,0x10(%esi)
0x0000000081c1832d:  movaps %xmm2,0x20(%esi)
0x0000000081c18331:  movaps %xmm3,0x30(%esi)
0x0000000081c18335:  movaps %xmm4,0x40(%esi)

which points to MOVAPS instruction currently no emulated by KVM.
Fix it by adding appropriate entries to opcode table in KVM's emulator.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
 arch/x86/kvm/emulate.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 07ffca0..a26d075 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3668,6 +3668,10 @@ static const struct gprefix pfx_vmovntpx = {
 	I(0, em_mov), N, N, N,
 };
 
+static const struct gprefix pfx_0f_28_0f_29 = {
+	I(Aligned, em_mov), N, N, N,
+};
+
 static const struct escape escape_d9 = { {
 	N, N, N, N, N, N, N, I(DstMem, em_fnstcw),
 }, {
@@ -3870,7 +3874,9 @@ static const struct opcode twobyte_table[256] = {
 	IIP(ModRM | SrcMem | Priv | Op3264, em_cr_write, cr_write, check_cr_write),
 	IIP(ModRM | SrcMem | Priv | Op3264, em_dr_write, dr_write, check_dr_write),
 	N, N, N, N,
-	N, N, N, GP(ModRM | DstMem | SrcReg | Sse | Mov | Aligned, &pfx_vmovntpx),
+	GP(ModRM | DstReg | SrcMem | Mov | Sse, &pfx_0f_28_0f_29),
+	GP(ModRM | DstMem | SrcReg | Mov | Sse, &pfx_0f_28_0f_29),
+	N, GP(ModRM | DstMem | SrcReg | Sse | Mov | Aligned, &pfx_vmovntpx),
 	N, N, N, N,
 	/* 0x30 - 0x3F */
 	II(ImplicitOps | Priv, em_wrmsr, wrmsr),
-- 
1.8.5.3

[PATCH 2/2] KVM: x86 emulator: emulate MOVAPD

[Igor Mammedov]

Add emulation for 0x66 prefixed instruction of 0f 28 opcode
that has been added earlier.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
 arch/x86/kvm/emulate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index a26d075..205b17e 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3669,7 +3669,7 @@ static const struct gprefix pfx_vmovntpx = {
 };
 
 static const struct gprefix pfx_0f_28_0f_29 = {
-	I(Aligned, em_mov), N, N, N,
+	I(Aligned, em_mov), I(Aligned, em_mov), N, N,
 };
 
 static const struct escape escape_d9 = { {
-- 
1.8.5.3

Re: [PATCH 0/2] KVM: x86 emulator: emulate MOVAPS and MOVAPD SSE instructions

[H. Peter Anvin]

MOVAPS, MOVAPD, and MOVDQA are the same operation.  They may, architecturally, have different performance characteristics, but nothing that would affect an emulator.

On March 15, 2014 1:01:58 PM PDT, Igor Mammedov <imammedo@redhat.com> wrote:
>MS HCK test fails on 32-bit Windows 8.1 due to missing MOVAPS
>instruction emulation, this series adds it and while at it,
>it adds emulation of MOVAPD which is trivial to implement on
>top of MOVAPS.
>
>Igor Mammedov (2):
>  KVM: x86 emulator: emulate MOVAPS
>  KVM: x86 emulator: emulate MOVAPD
>
> arch/x86/kvm/emulate.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.

Re: [PATCH 0/2] KVM: x86 emulator: emulate MOVAPS and MOVAPD SSE instructions

[H. Peter Anvin]

Stupid question... what instructions do NOT need emulsion in KVM? It would seem that at least anything that touches memory would?

On March 15, 2014 1:01:58 PM PDT, Igor Mammedov <imammedo@redhat.com> wrote:
>MS HCK test fails on 32-bit Windows 8.1 due to missing MOVAPS
>instruction emulation, this series adds it and while at it,
>it adds emulation of MOVAPD which is trivial to implement on
>top of MOVAPS.
>
>Igor Mammedov (2):
>  KVM: x86 emulator: emulate MOVAPS
>  KVM: x86 emulator: emulate MOVAPD
>
> arch/x86/kvm/emulate.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.

Re: [PATCH 0/2] KVM: x86 emulator: emulate MOVAPS and MOVAPD SSE instructions

[Paolo Bonzini]

Il 15/03/2014 23:42, H. Peter Anvin ha scritto:
> Stupid question... what instructions do NOT need emulsion in KVM? It would seem that at least anything that touches memory would?

Yes, indeed.  Anything that touches memory can be used on MMIO and then 
needs emulation.

Paolo

> On March 15, 2014 1:01:58 PM PDT, Igor Mammedov <imammedo@redhat.com> wrote:
>> MS HCK test fails on 32-bit Windows 8.1 due to missing MOVAPS
>> instruction emulation, this series adds it and while at it,
>> it adds emulation of MOVAPD which is trivial to implement on
>> top of MOVAPS.
>>
>> Igor Mammedov (2):
>>  KVM: x86 emulator: emulate MOVAPS
>>  KVM: x86 emulator: emulate MOVAPD
>>
>> arch/x86/kvm/emulate.c | 8 +++++++-
>> 1 file changed, 7 insertions(+), 1 deletion(-)
>

Re: [PATCH 0/2] KVM: x86 emulator: emulate MOVAPS and MOVAPD SSE instructions

[Paolo Bonzini]

Il 15/03/2014 21:01, Igor Mammedov ha scritto:
> MS HCK test fails on 32-bit Windows 8.1 due to missing MOVAPS
> instruction emulation, this series adds it and while at it,
> it adds emulation of MOVAPD which is trivial to implement on
> top of MOVAPS.
>
> Igor Mammedov (2):
>   KVM: x86 emulator: emulate MOVAPS
>   KVM: x86 emulator: emulate MOVAPD
>
>  arch/x86/kvm/emulate.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>

Applied both to kvm/next, thanks.

Paolo

Re: [PATCH 0/2] KVM: x86 emulator: emulate MOVAPS and MOVAPD SSE instructions

[Paolo Bonzini]

Il 15/03/2014 23:39, H. Peter Anvin ha scritto:
> MOVAPS, MOVAPD, and MOVDQA are the same operation.  They may, architecturally, have different performance characteristics, but nothing that would affect an emulator.

In fact MOVAPS and MOVAPD are implemented the same way in this patch:

I(Aligned, em_mov), I(Aligned, em_mov), N, N,

These are respectively for no prefix, 0x66, 0xf2 and 0xf3.  MOVDQA was 
already implemented, but on AMD some memcpy implementations use MOVAPS 
because it's a byte shorter.

Paolo

> On March 15, 2014 1:01:58 PM PDT, Igor Mammedov <imammedo@redhat.com> wrote:
>> MS HCK test fails on 32-bit Windows 8.1 due to missing MOVAPS
>> instruction emulation, this series adds it and while at it,
>> it adds emulation of MOVAPD which is trivial to implement on
>> top of MOVAPS.
>>
>> Igor Mammedov (2):
>>  KVM: x86 emulator: emulate MOVAPS
>>  KVM: x86 emulator: emulate MOVAPD
>>
>> arch/x86/kvm/emulate.c | 8 +++++++-
>> 1 file changed, 7 insertions(+), 1 deletion(-)
>

Re: [PATCH 0/2] KVM: x86 emulator: emulate MOVAPS and MOVAPD SSE instructions

[H. Peter Anvin]

After seeing the sheer number of one-off additions, I'm wondering if going through the opcode map systematically and see what is still missing might not be a bad idea.

On March 17, 2014 2:30:43 AM PDT, Paolo Bonzini <pbonzini@redhat.com> wrote:
>Il 15/03/2014 23:42, H. Peter Anvin ha scritto:
>> Stupid question... what instructions do NOT need emulsion in KVM? It
>would seem that at least anything that touches memory would?
>
>Yes, indeed.  Anything that touches memory can be used on MMIO and then
>
>needs emulation.
>
>Paolo
>
>> On March 15, 2014 1:01:58 PM PDT, Igor Mammedov <imammedo@redhat.com>
>wrote:
>>> MS HCK test fails on 32-bit Windows 8.1 due to missing MOVAPS
>>> instruction emulation, this series adds it and while at it,
>>> it adds emulation of MOVAPD which is trivial to implement on
>>> top of MOVAPS.
>>>
>>> Igor Mammedov (2):
>>>  KVM: x86 emulator: emulate MOVAPS
>>>  KVM: x86 emulator: emulate MOVAPD
>>>
>>> arch/x86/kvm/emulate.c | 8 +++++++-
>>> 1 file changed, 7 insertions(+), 1 deletion(-)
>>

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.

Re: [PATCH 0/2] KVM: x86 emulator: emulate MOVAPS and MOVAPD SSE instructions

[Paolo Bonzini]

Il 17/03/2014 16:16, H. Peter Anvin ha scritto:
> After seeing the sheer number of one-off additions, I'm wondering if going through the opcode map systematically and see what is still missing might not be a bad idea.

Memory access instructions always need emulation, but there aren't that 
many left.  There are some, such as MOVUPS/MOVUPD.

However, this is not the only use of emulation.  The problem stems from 
pre-Westmere Intel chips that didn't have unrestricted mode 
virtualization.  For these chips, you need to emulate all instructions 
that might be used in protected mode transitions and also, possibly, in 
big real mode.  In practice you will rarely see big real mode (the main 
exception is option ROMs, due to PMM), still every OS likes to do 
something different in their protected mode transitions so this is the 
source of most one-off additions that you have seen.

Until around 3.6, KVM used to transform big real mode into a "good" real 
mode that the processor would like, while breaking completely in big 
real mode; this is now emulate_invalid_guest_state=N.  Nowadays, it uses 
emulation, which is emulate_invalid_guest_state=Y.  As you can imagine 
it's quite slow (though some performance can certainly be scraped off 
the emulator).

If CS and possibly SS are valid real mode selectors, it should be 
possible to run big real mode at almost-full speed, taking exits only 
for memory accesses via other segment registers.  It is on my todo list, 
but not very high.  Depending on the exit overhead, it may be a better 
idea to revert the emulate_invalid_guest_state default to N and let 
people who care about big real mode specify Y.

Paolo

> On March 17, 2014 2:30:43 AM PDT, Paolo Bonzini <pbonzini@redhat.com> wrote:
>> Il 15/03/2014 23:42, H. Peter Anvin ha scritto:
>>> Stupid question... what instructions do NOT need emulsion in KVM? It
>> would seem that at least anything that touches memory would?
>>
>> Yes, indeed.  Anything that touches memory can be used on MMIO and then
>>
>> needs emulation.
>>
>> Paolo
>>
>>> On March 15, 2014 1:01:58 PM PDT, Igor Mammedov <imammedo@redhat.com>
>> wrote:
>>>> MS HCK test fails on 32-bit Windows 8.1 due to missing MOVAPS
>>>> instruction emulation, this series adds it and while at it,
>>>> it adds emulation of MOVAPD which is trivial to implement on
>>>> top of MOVAPS.
>>>>
>>>> Igor Mammedov (2):
>>>>  KVM: x86 emulator: emulate MOVAPS
>>>>  KVM: x86 emulator: emulate MOVAPD
>>>>
>>>> arch/x86/kvm/emulate.c | 8 +++++++-
>>>> 1 file changed, 7 insertions(+), 1 deletion(-)
>>>
>

Re: [PATCH 0/2] KVM: x86 emulator: emulate MOVAPS and MOVAPD SSE instructions

[H. Peter Anvin]

On 03/17/2014 10:01 AM, Paolo Bonzini wrote:
> the emulator).
> 
> If CS and possibly SS are valid real mode selectors, it should be
> possible to run big real mode at almost-full speed, taking exits only
> for memory accesses via other segment registers.  It is on my todo list,
> but not very high.  Depending on the exit overhead, it may be a better
> idea to revert the emulate_invalid_guest_state default to N and let
> people who care about big real mode specify Y.
> 

I'm not sure what you mean with "valid real mode selectors"; the normal
case in big real mode is that either CS = SS = 0 or CS = SS = <some
program base address>.

As Big Real Mode is part of the spec for certain things (option ROMs, as
we discussed) it probably matters, but especially with the CPUs not
supporting unrestricted mode fading into history I suspect it is fine
for BRM to be slow on those older processors.

The PM transitions that you mentioned are usually only a handful of
instructions and thus can be slow.

	-hpa

Re: [PATCH 0/2] KVM: x86 emulator: emulate MOVAPS and MOVAPD SSE instructions

[Paolo Bonzini]

Il 17/03/2014 18:38, H. Peter Anvin ha scritto:
> I'm not sure what you mean with "valid real mode selectors"; the normal
> case in big real mode is that either CS = SS = 0 or CS = SS = <some
> program base address>.

I mean "valid according to the VMX spec" for running in vm86 mode: base 
= selector << 4, limit = 0xffff, access rights = 0xf3.

If a segment does not follow the rules, but CS does, we could run the 
guest normally and trap memory accesses to KVM.

Paolo