>-----Original Message-----
>From: Jason Wang <jasow...@redhat.com>
>Subject: Re: [PATCH v3 14/17] intel_iommu: Set default aw_bits to 48 in
>scalable modern mode
>
>On Wed, Sep 11, 2024 at 1:27 PM Zhenzhong Duan
><zhenzhong.d...@intel.com> wrote:
>>
>> 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.d...@intel.com>
>> Reviewed-by: Clément Mathieu--Drif<clement.mathieu--d...@eviden.com>
>> ---
>> include/hw/i386/intel_iommu.h | 2 +-
>> hw/i386/intel_iommu.c | 10 +++++++++-
>> 2 files changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/hw/i386/intel_iommu.h
>b/include/hw/i386/intel_iommu.h
>> index b843d069cc..48134bda11 100644
>> --- a/include/hw/i386/intel_iommu.h
>> +++ b/include/hw/i386/intel_iommu.h
>> @@ -45,7 +45,7 @@ OBJECT_DECLARE_SIMPLE_TYPE(IntelIOMMUState,
>INTEL_IOMMU_DEVICE)
>> #define DMAR_REG_SIZE 0x230
>> #define VTD_HOST_AW_39BIT 39
>> #define VTD_HOST_AW_48BIT 48
>> -#define VTD_HOST_ADDRESS_WIDTH VTD_HOST_AW_39BIT
>> +#define VTD_HOST_AW_AUTO 0xff
>> #define VTD_HAW_MASK(aw) ((1ULL << (aw)) - 1)
>>
>> #define DMAR_REPORT_F_INTR (1)
>> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
>> index c25211ddaf..949f120456 100644
>> --- a/hw/i386/intel_iommu.c
>> +++ b/hw/i386/intel_iommu.c
>> @@ -3771,7 +3771,7 @@ 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),
>> + VTD_HOST_AW_AUTO),
>
>Such command line API seems to be wired.
>
>I think we can stick the current default and when scalable modern is
>enabled by aw is not specified, we can change aw to 48?
Current default is 39. I use VTD_HOST_AW_AUTO to initialize aw as not specified.
Do we have other way to catch the update if we stick to 39?
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),
>> @@ -4686,6 +4686,14 @@ static bool
>vtd_decide_config(IntelIOMMUState *s, Error **errp)
>> }
>> }
>>
>> + if (s->aw_bits == VTD_HOST_AW_AUTO) {
>> + 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) {
>> --
>> 2.34.1
>>
>
>Thanks
