>unnecessary divergence is
> undesirable.
Good point, we should keep kvm/ia64 and xen/ia64 the same code base as
possible.
Anthony
Isaku Yamahata wrote:
> Hi Jes.
>
> Good catch.
> I thought similar fix is necessary for xen/ia64 and checked the code.
> It was fixed differently. I think the unnecessary divergence is
> undesirable.
> What do you think the following fix according?
>
>
> Only copy in the data actually requested by the instruction emulation
> and zero pad the destination register first. This avoids the problem
> where emulated mmio access got garbled data from ld2.acq instructions
> in the vga console driver.
>
> Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>
> Cc: Jes Sorensen <jes@xxxxxxx>
>
> diff --git a/arch/ia64/kvm/mmio.c b/arch/ia64/kvm/mmio.c
> index 351bf70..e6f194a 100644
> --- a/arch/ia64/kvm/mmio.c
> +++ b/arch/ia64/kvm/mmio.c
> @@ -154,6 +154,9 @@ static void mmio_access(struct kvm_vcpu *vcpu,
> u64 src_pa, u64 *dest, p->u.ioreq.dir = dir;
> if (dir == IOREQ_WRITE)
> p->u.ioreq.data = *dest;
> + else
> + /* it's necessary to ensure zero extending */
> + p->u.ioreq.data = 0;
> p->u.ioreq.state = STATE_IOREQ_READY;
> vmm_transition(vcpu);
>
>
>
> On Tue, May 20, 2008 at 01:13:50PM +0200, Jes Sorensen wrote:
>> Matthew Chapman wrote:
>>> Jes,
>>>
>>> Glad you tracked it down. Can I suggest rather than using memcpy, a
>>> more efficient way might be something like...
>>>
>>> #define ZERO_EXTEND(x,bits) ((x) & (~0UL >> (64-(bits))))
>>>
>>> *dest = ZERO_EXTEND(p->u.ioreq.data, 8*s);
>>
>> Much nicer indeed!
>>
>> Here's a pretty version - Tony will you apply this one instead.
>>
>> Cheers,
>> Jes
>>
>>
>
>> Only copy in the data actually requested by the instruction emulation
>> and zero pad the destination register first. This avoids the problem
>> where emulated mmio access got garbled data from ld2.acq
>> instructions in the vga console driver.
>>
>> Signed-off-by: Jes Sorensen <jes@xxxxxxx>
>>
>> ---
>> arch/ia64/kvm/mmio.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> Index: linux-2.6.git/arch/ia64/kvm/mmio.c
>> ===================================================================
>> --- linux-2.6.git.orig/arch/ia64/kvm/mmio.c
>> +++ linux-2.6.git/arch/ia64/kvm/mmio.c
>> @@ -159,7 +159,8 @@
>>
>> if (p->u.ioreq.state == STATE_IORESP_READY) {
>> if (dir == IOREQ_READ)
>> - *dest = p->u.ioreq.data;
>> + /* it's necessary to ensure zero extending */
>> + *dest = p->u.ioreq.data & (~0UL >> (64-(s*8)));
} else
>> panic_vm(vcpu);
>> out:
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