Re: [PATCH rfcv2 15/17] intel_iommu: Set default aw_bits to 48 in scalable modren mode

[CLEMENT MATHIEU--DRIF <clement.mathieu--drif@eviden.com>]

On 27/05/2024 05:16, Duan, Zhenzhong wrote:
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>
>
> Hi Clement,
>
>> -----Original Message-----
>> From: CLEMENT MATHIEU--DRIF <clement.mathieu--drif@eviden.com>
>> Sent: Friday, May 24, 2024 9:57 PM
>> To: Duan, Zhenzhong <zhenzhong.duan@intel.com>; qemu-
>> devel@nongnu.org
>> Cc: alex.williamson@redhat.com; clg@redhat.com; eric.auger@redhat.com;
>> mst@redhat.com; peterx@redhat.com; jasowang@redhat.com;
>> jgg@nvidia.com; nicolinc@nvidia.com; joao.m.martins@oracle.com; Tian,
>> Kevin <kevin.tian@intel.com>; Liu, Yi L <yi.l.liu@intel.com>; Peng, Chao P
>> <chao.p.peng@intel.com>; Paolo Bonzini <pbonzini@redhat.com>; Richard
>> Henderson <richard.henderson@linaro.org>; Eduardo Habkost
>> <eduardo@habkost.net>; Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
>> Subject: Re: [PATCH rfcv2 15/17] intel_iommu: Set default aw_bits to 48 in
>> scalable modren mode
>>
>> Hi Zhenzhong
>>
>> On 22/05/2024 08:23, Zhenzhong Duan wrote:
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>> email comes from a known sender and you know the content is safe.
>>>
>>> According to VTD spec, stage-1 page table could support 4-level and
>>> 5-level paging.
>>>
>>> However, 5-level paging translation emulation is unsupported yet.
>>> That means the only supported value for aw_bits is 48.
>>>
>>> So default aw_bits to 48 in scalable modern mode. In other cases,
>>> it is still default to 39 for compatibility.
>>>
>>> Add a check to ensure user specified value is 48 in modern mode
>>> for now.
>>>
>>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>>> ---
>>>    hw/i386/intel_iommu.c | 16 +++++++++++++++-
>>>    1 file changed, 15 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
>>> index e07daaba99..a4c241ea96 100644
>>> --- a/hw/i386/intel_iommu.c
>>> +++ b/hw/i386/intel_iommu.c
>>> @@ -3748,7 +3748,7 @@ static Property vtd_properties[] = {
>>>                                ON_OFF_AUTO_AUTO),
>>>        DEFINE_PROP_BOOL("x-buggy-eim", IntelIOMMUState, buggy_eim,
>> false),
>>>        DEFINE_PROP_UINT8("aw-bits", IntelIOMMUState, aw_bits,
>>> -                      VTD_HOST_ADDRESS_WIDTH),
>>> +                      0xff),
>> you could define a constant for this invalid value
> Sure, maybe VTD_HOST_ADDRESS_WIDTH_UNDEFINED?
Yes, fine for me
>
> Thanks
> Zhenzhong
>
>>>        DEFINE_PROP_BOOL("caching-mode", IntelIOMMUState, caching_mode,
>> FALSE),
>>>        DEFINE_PROP_BOOL("x-scalable-mode", IntelIOMMUState,
>> scalable_mode, FALSE),
>>>        DEFINE_PROP_BOOL("snoop-control", IntelIOMMUState,
>> snoop_control, false),
>>> @@ -4663,6 +4663,14 @@ static bool
>> vtd_decide_config(IntelIOMMUState *s, Error **errp)
>>>            }
>>>        }
>>>
>>> +    if (s->aw_bits == 0xff) {
>>> +        if (s->scalable_modern) {
>>> +            s->aw_bits = VTD_HOST_AW_48BIT;
>>> +        } else {
>>> +            s->aw_bits = VTD_HOST_AW_39BIT;
>>> +        }
>>> +    }
>>> +
>>>        if ((s->aw_bits != VTD_HOST_AW_39BIT) &&
>>>            (s->aw_bits != VTD_HOST_AW_48BIT) &&
>>>            !s->scalable_modern) {
>>> @@ -4671,6 +4679,12 @@ static bool
>> vtd_decide_config(IntelIOMMUState *s, Error **errp)
>>>            return false;
>>>        }
>>>
>>> +    if ((s->aw_bits != VTD_HOST_AW_48BIT) && s->scalable_modern) {
>>> +        error_setg(errp, "Supported values for aw-bits are: %d",
>> specify 'in modern mode' in the message?
>>> +                   VTD_HOST_AW_48BIT);
>>> +        return false;
>>> +    }
>>> +
>>>        if (s->scalable_mode && !s->dma_drain) {
>>>            error_setg(errp, "Need to set dma_drain for scalable mode");
>>>            return false;
>>> --
>>> 2.34.1
>>>
>> #cmd