RE: [PATCH v1 16/17] intel_iommu: Modify x-scalable-mode to be string option

[Duan, Zhenzhong]

>-----Original Message-----
>From: CLEMENT MATHIEU--DRIF <clement.mathieu--drif@eviden.com>
>Subject: Re: [PATCH v1 16/17] intel_iommu: Modify x-scalable-mode to be
>string option
>
>
>
>On 18/07/2024 10:16, 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.
>>
>>
>> From: Yi Liu <yi.l.liu@intel.com>
>>
>> Intel VT-d 3.0 introduces scalable mode, and it has a bunch of capabilities
>> related to scalable mode translation, thus there are multiple combinations.
>> While this vIOMMU implementation wants to simplify it for user by
>providing
>> typical combinations. User could config it by "x-scalable-mode" option. The
>> usage is as below:
>>
>> "-device intel-iommu,x-scalable-mode=["legacy"|"modern"|"off"]"
>>
>>   - "legacy": gives support for stage-2 page table
>>   - "modern": gives support for stage-1 page table
>>   - "off": no scalable mode support
>>   -  if not configured, means no scalable mode support, if not proper
>>      configured, will throw error
>s/proper/properly
>Maybe we could split and rephrase the last bullet point to make it clear
>that "off" is equivalent to not using the option at all

You mean split last bullet as a separate paragraph?
Then what about below:

  - "legacy": gives support for stage-2 page table
  - "modern": gives support for stage-1 page table
  - "off": no scalable mode support
  -  any other string, will throw error

If x-scalable-mode is not configured, it is equivalent to x-scalable-mode=off.

Thanks
Zhenzhong

>>
>> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
>> Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>> ---
>>   include/hw/i386/intel_iommu.h |  1 +
>>   hw/i386/intel_iommu.c         | 24 +++++++++++++++++++++++-
>>   2 files changed, 24 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/hw/i386/intel_iommu.h
>b/include/hw/i386/intel_iommu.h
>> index 48134bda11..650641544c 100644
>> --- a/include/hw/i386/intel_iommu.h
>> +++ b/include/hw/i386/intel_iommu.h
>> @@ -263,6 +263,7 @@ struct IntelIOMMUState {
>>
>>       bool caching_mode;              /* RO - is cap CM enabled? */
>>       bool scalable_mode;             /* RO - is Scalable Mode supported? */
>> +    char *scalable_mode_str;        /* RO - admin's Scalable Mode config */
>>       bool scalable_modern;           /* RO - is modern SM supported? */
>>       bool snoop_control;             /* RO - is SNP filed supported? */
>>
>> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
>> index 2804c3628a..14d05fce1d 100644
>> --- a/hw/i386/intel_iommu.c
>> +++ b/hw/i386/intel_iommu.c
>> @@ -3770,7 +3770,7 @@ static Property vtd_properties[] = {
>>       DEFINE_PROP_UINT8("aw-bits", IntelIOMMUState, aw_bits,
>>                         VTD_HOST_AW_AUTO),
>>       DEFINE_PROP_BOOL("caching-mode", IntelIOMMUState, caching_mode,
>FALSE),
>> -    DEFINE_PROP_BOOL("x-scalable-mode", IntelIOMMUState,
>scalable_mode, FALSE),
>> +    DEFINE_PROP_STRING("x-scalable-mode", IntelIOMMUState,
>scalable_mode_str),
>>       DEFINE_PROP_BOOL("snoop-control", IntelIOMMUState,
>snoop_control, false),
>>       DEFINE_PROP_BOOL("x-pasid-mode", IntelIOMMUState, pasid, false),
>>       DEFINE_PROP_BOOL("dma-drain", IntelIOMMUState, dma_drain, true),
>> @@ -4686,6 +4686,28 @@ static bool
>vtd_decide_config(IntelIOMMUState *s, Error **errp)
>>           }
>>       }
>>
>> +    if (s->scalable_mode_str &&
>> +        (strcmp(s->scalable_mode_str, "off") &&
>> +         strcmp(s->scalable_mode_str, "modern") &&
>> +         strcmp(s->scalable_mode_str, "legacy"))) {
>> +        error_setg(errp, "Invalid x-scalable-mode config,"
>> +                         "Please use \"modern\", \"legacy\" or \"off\"");
>> +        return false;
>> +    }
>> +
>> +    if (s->scalable_mode_str &&
>> +        !strcmp(s->scalable_mode_str, "legacy")) {
>> +        s->scalable_mode = true;
>> +        s->scalable_modern = false;
>> +    } else if (s->scalable_mode_str &&
>> +        !strcmp(s->scalable_mode_str, "modern")) {
>> +        s->scalable_mode = true;
>> +        s->scalable_modern = true;
>> +    } else {
>> +        s->scalable_mode = false;
>> +        s->scalable_modern = false;
>> +    }
>> +
>>       if (s->aw_bits == VTD_HOST_AW_AUTO) {
>>           if (s->scalable_modern) {
>>               s->aw_bits = VTD_HOST_AW_48BIT;
>> --
>> 2.34.1
>>
>LGTM