Re: [Xen-devel] [PATCH v1 05/10] iommu/arm: Re-define iommu_use_hap_pt(d) as iommu_hap_pt_share

[Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>]

On Thu, May 11, 2017 at 8:58 PM, Julien Grall <julien.grall@xxxxxxx> wrote:
>
>
> On 11/05/17 15:38, Oleksandr Tyshchenko wrote:
>>
>> On Thu, May 11, 2017 at 2:28 PM, Julien Grall <julien.grall@xxxxxxx>
>> wrote:
>>>
>>> Hi Oleksandr,
>>
>> Hi Julien
>
>
> Hi Oleksandr,
>
>
>>>
>>> On 10/05/17 15:03, Oleksandr Tyshchenko wrote:
>>>>
>>>>
>>>> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
>>>>
>>>> Not every integrated into ARM SoCs IOMMU can share page tables
>>>> with the CPU and as result the iommu_use_hap_pt(d) is not always true.
>>>> Reuse x86's iommu_hap_pt_share flag to indicate whether the IOMMU
>>>> page table is shared or not.
>>>>
>>>> Now all IOMMU drivers on ARM are able to change this flag
>>>> according to their possibilities like x86-variants do.
>>>> Therefore set iommu_hap_pt_share flag for SMMU because it always shares
>>>> page table with the CPU.
>>>>
>>>> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
>>>> ---
>>>>  xen/drivers/passthrough/arm/smmu.c | 3 +++
>>>>  xen/include/asm-arm/iommu.h        | 7 +++++--
>>>>  2 files changed, 8 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/xen/drivers/passthrough/arm/smmu.c
>>>> b/xen/drivers/passthrough/arm/smmu.c
>>>> index 527a592..86ee12a 100644
>>>> --- a/xen/drivers/passthrough/arm/smmu.c
>>>> +++ b/xen/drivers/passthrough/arm/smmu.c
>>>> @@ -2870,6 +2870,9 @@ static __init int arm_smmu_dt_init(struct
>>>> dt_device_node *dev,
>>>>
>>>>         platform_features &= smmu->features;
>>>>
>>>> +       /* Always share P2M table between the CPU and the SMMU */
>>>> +       iommu_hap_pt_share = true;
>>>> +
>>>
>>>
>>>
>>> I would prefer to bail-out if someone try to unshare the page-table
>>> rather
>>> than overriding. This would help us to know if someone are try to do
>>> that.
>>>
>>> So I would do:
>>>
>>> if ( !iommu_hap_pt_share )
>>> {
>>>         printk(....)
>>>         return -EINVAL;
>>> }
>>
>> I got it for SMMU.
>>
>> But, for IPMMU we will override since iommu_hap_pt_share is true by
>> default. Right?
>>
>> /*
>> * The IPMMU can't reuse P2M table since it only supports
>> * stage-1 page tables.
>> */
>> iommu_hap_pt_share = false;
>
>
> Good point. Looking at the other driver, they print a message to notify the
> override. (See drivers/passthrough/amd/iommu_init.c for instance).
I will print a message too.

>
> Cheers,
>
> --
> Julien Grall



-- 
Regards,

Oleksandr Tyshchenko

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel