Re: [PATCH v2 03/17] intel_iommu: Add a placeholder variable for scalable modern mode

["Duan, Zhenzhong" <zhenzhong.duan@intel.com>]

On 8/6/2024 2:35 PM, CLEMENT MATHIEU--DRIF wrote:
>
> On 05/08/2024 08:27, Zhenzhong Duan wrote:
>> Caution: External email. Do not open attachments or click links, unless this email comes from a known sender and you know the content is safe.
>>
>>
>> Add an new element scalable_mode in IntelIOMMUState to mark scalable
>> modern mode, this element will be exposed as an intel_iommu property
>> finally.
>>
>> For now, it's only a placehholder and used for address width
>> compatibility check and block host device passthrough until nesting
>> is supported.
>>
>> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>> ---
>>    include/hw/i386/intel_iommu.h |  1 +
>>    hw/i386/intel_iommu.c         | 12 +++++++++---
>>    2 files changed, 10 insertions(+), 3 deletions(-)
>>
>> diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h
>> index 1eb05c29fc..788ed42477 100644
>> --- a/include/hw/i386/intel_iommu.h
>> +++ b/include/hw/i386/intel_iommu.h
>> @@ -262,6 +262,7 @@ struct IntelIOMMUState {
>>
>>        bool caching_mode;              /* RO - is cap CM enabled? */
>>        bool scalable_mode;             /* RO - is Scalable Mode supported? */
>> +    bool scalable_modern;           /* RO - is modern SM supported? */
>>        bool snoop_control;             /* RO - is SNP filed supported? */
>>
>>        dma_addr_t root;                /* Current root table pointer */
>> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
>> index e3465fc27d..c1382a5651 100644
>> --- a/hw/i386/intel_iommu.c
>> +++ b/hw/i386/intel_iommu.c
>> @@ -3872,7 +3872,13 @@ static bool vtd_check_hiod(IntelIOMMUState *s, HostIOMMUDevice *hiod,
>>            return false;
>>        }
>>
>> -    return true;
>> +    if (!s->scalable_modern) {
>> +        /* All checks requested by VTD non-modern mode pass */
>> +        return true;
>> +    }
>> +
>> +    error_setg(errp, "host device is unsupported in scalable modern mode yet");
>> +    return false;
>>    }
>>
>>    static bool vtd_dev_set_iommu_device(PCIBus *bus, void *opaque, int devfn,
>> @@ -4262,9 +4268,9 @@ static bool vtd_decide_config(IntelIOMMUState *s, Error **errp)
>>            }
>>        }
>>
>> -    /* Currently only address widths supported are 39 and 48 bits */
>>        if ((s->aw_bits != VTD_HOST_AW_39BIT) &&
>> -        (s->aw_bits != VTD_HOST_AW_48BIT)) {
>> +        (s->aw_bits != VTD_HOST_AW_48BIT) &&
>> +        !s->scalable_modern) {
> Why does scalable_modern allow to use a value other than 39 or 48?
> Is it safe?

The check for scalable_modern is in patch14:

if ((s->aw_bits != VTD_HOST_AW_48BIT) && s->scalable_modern) {

error_setg(errp, "Supported values for aw-bits are: %d", VTD_HOST_AW_48BIT);

return false;

}

Let me know if you prefer to move it in this patch.

Thanks

Zhenzhong