On 8/8/10, Avi Kivity <avi@xxxxxxxxxx> wrote:
> On 08/08/2010 07:53 AM, Mohammed Gamal wrote:
>> On Sun, Aug 8, 2010 at 2:34 PM, Avi Kivity<avi@xxxxxxxxxx> wrote:
>>> On 08/08/2010 05:27 AM, Mohammed Gamal wrote:
>>>> This adds unary mul, imul, div, and idiv instructions (group 3 r/m 4-7).
>>>>
>>>> Signed-off-by: Mohammed Gamal<m.gamal005@xxxxxxxxx>
>>>> ---
>>>> arch/x86/kvm/emulate.c | 41
>>>> ++++++++++++++++++++++++++++++++++++++++-
>>>> 1 files changed, 40 insertions(+), 1 deletions(-)
>>>>
>>>> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
>>>> index 7d78832..6d1ec53 100644
>>>> --- a/arch/x86/kvm/emulate.c
>>>> +++ b/arch/x86/kvm/emulate.c
>>>> @@ -315,6 +315,31 @@ struct group_dual {
>>>> }
>>>> \
>>>> } while (0)
>>>>
>>>> +#define __emulate_1op_src(_op, _src, _ax, _dx, _eflags, _suffix)
>>>> \
>>> Not just 1op - add rax_rdx to the name to indicate these are implicit
>>> operands.
>>>
>>>> + do {
>>>> \
>>>> + unsigned long _tmp;
>>>> \
>>>> +
>>>> \
>>>> + __asm__ __volatile__ (
>>>> \
>>>> + _PRE_EFLAGS("0", "4", "1")
>>>> \
>>>> + _op _suffix " %5; "
>>>> \
>>>> + _POST_EFLAGS("0", "4", "1")
>>>> \
>>>> + : "=m" (_eflags), "=&r" (_tmp),
>>>> \
>>>> + "=a" (_ax), "=d" (_dx)
>>>> \
>>>> + : "i" (EFLAGS_MASK), "m" ((_src).val),
>>>> \
>>>> + "a" (_ax), "d" (_dx));
>>>> \
>>>> + } while (0)
>>> The byte form of the instruction doesn't update dx, and the word form
>>> doesn't update edx[16:31]. So the "=a" and "=d" operands need to be "+a"
>>> and "+d" so the compiler loads them before the operation is started.
>>>
>
> I see you have "a" and "d" also in the inputs section. So the code is
> correct.
>
>>> Please add a test to the effect, for example start with eax=0x12345678,
>>> and
>>> multiply (byte size) 0x80 by 0x40,
>> We already have a value store in eax, so I can only either multiply it
>> by 0x80 or 0x40. Or do you mean we should have eax=0x12345680 and then
>> perhaps multply by 0x40 and make sure the upper 16 bits are preserved?
>
> Yes.
>
Cool. I already sent out a new test that does this.
> --
> I have a truly marvellous patch that fixes the bug which this
> signature is too narrow to contain.
>
>
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