RE: [PATCH] drm/amdgpu: add print for iommu translation mode

["Sider, Graham" <Graham.Sider@amd.com>]

[Public]

> -----Original Message-----
> From: Kuehling, Felix <Felix.Kuehling@amd.com>
> Sent: Friday, March 17, 2023 5:16 PM
> To: Sider, Graham <Graham.Sider@amd.com>; Russell, Kent
> <Kent.Russell@amd.com>; Mahfooz, Hamza <Hamza.Mahfooz@amd.com>;
> amd-gfx@lists.freedesktop.org
> Subject: Re: [PATCH] drm/amdgpu: add print for iommu translation mode
> 
> On 2023-03-17 16:04, Sider, Graham wrote:
> > [AMD Official Use Only - General]
> >
> >
> >
> >> -----Original Message-----
> >> From: Russell, Kent <Kent.Russell@amd.com>
> >> Sent: Friday, March 17, 2023 3:58 PM
> >> To: Mahfooz, Hamza <Hamza.Mahfooz@amd.com>; Sider, Graham
> >> <Graham.Sider@amd.com>; amd-gfx@lists.freedesktop.org
> >> Cc: Kuehling, Felix <Felix.Kuehling@amd.com>
> >> Subject: RE: [PATCH] drm/amdgpu: add print for iommu translation mode
> >>
> >> [AMD Official Use Only - General]
> >>
> >>
> >>
> >>> -----Original Message-----
> >>> From: amd-gfx <amd-gfx-bounces@lists.freedesktop.org> On Behalf Of
> >>> Hamza Mahfooz
> >>> Sent: Friday, March 17, 2023 3:58 PM
> >>> To: Sider, Graham <Graham.Sider@amd.com>;
> >>> amd-gfx@lists.freedesktop.org
> >>> Cc: Kuehling, Felix <Felix.Kuehling@amd.com>
> >>> Subject: Re: [PATCH] drm/amdgpu: add print for iommu translation
> >>> mode
> >>>
> >>>
> >>> On 3/17/23 15:47, Graham Sider wrote:
> >>>> Add log to display whether RAM is direct vs DMA mapped.
> >>>>
> >>>> Signed-off-by: Graham Sider <Graham.Sider@amd.com>
> >>> If this information is only useful for debugging purposes, please
> >>> use
> >>> drm_dbg() instead of pr_info().
> > It's useful for more than just debug I would say. Just a quick way to grep
> whether IOMMU is off/pt vs device isolation mode.
> 
> I agree. The kernel log otherwise tells you the default IOMMU domain, but it
> may not match the domain actually used for the GPU. Without this message
> there is no easy way to tell from a kernel log. This will help with triaging issues
> from logs provided by external and internal users.
> 
> 
> >
> > Graham
> >
> >>>> ---
> >>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 6 +++++-
> >>>>    1 file changed, 5 insertions(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> >>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> >>>> index 8bba5e6872a1..8797a9523244 100644
> >>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> >>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> >>>> @@ -3528,8 +3528,12 @@ static void
> >>> amdgpu_device_check_iommu_direct_map(struct amdgpu_device
> *adev)
> >>>>    	struct iommu_domain *domain;
> >>>>
> >>>>    	domain = iommu_get_domain_for_dev(adev->dev);
> >>>> -	if (!domain || domain->type == IOMMU_DOMAIN_IDENTITY)
> >>>> +	if (!domain || domain->type == IOMMU_DOMAIN_IDENTITY) {
> >>>> +		pr_info("RAM is direct mapped to GPU (not traslated by
> 
> Use dev_info. That way you can tell which GPU the message applies to in a
> multi-GPU system.
> 

Good point - will do that. Thanks!

Graham

> Regards,
>    Felix
> 
> 
> >> traslated -> translated
> >>
> > Thanks, my keyboard keeps skipping the on the 'n' key lately :( time for a
> clean.
> >
> > Graham
> >
> >>   Kent
> >>> IOMMU)\n");
> >>>>    		adev->ram_is_direct_mapped = true;
> >>>> +	} else {
> >>>> +		pr_info("RAM is DMA mapped to GPU (translated by
> >>> IOMMU)\n");
> >>>> +	}
> >>>>    }
> >>>>
> >>>>    static const struct attribute *amdgpu_dev_attributes[] = {
> >>> --
> >>> Hamza