Re: [PATCH] drm/i915/gt: Report full vm address range

[Nirmoy Das <nirmoy.das@linux.intel.com>]

On 3/14/2024 3:04 PM, Lionel Landwerlin wrote:
> Hi Andi,
>
> In Mesa we've been relying on I915_CONTEXT_PARAM_GTT_SIZE so as long 
> as that is adjusted by the kernel

What do you mean by adjusted by, should it be a aligned size?

I915_CONTEXT_PARAM_GTT_SIZE ioctl is returning vm->total which is 
adjusted(reduced by a page).

This patch might cause silent error as it is not removing WABB which is 
using the reserved page to add dummy blt and if userspace is using that

page then it will be overwritten.


Regards,

Nirmoy

> , we should be able to continue working without issues.
>
> Acked-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
>
> Thanks,
>
> -Lionel
>
> On 13/03/2024 21:39, Andi Shyti wrote:
>> Commit 9bb66c179f50 ("drm/i915: Reserve some kernel space per
>> vm") has reserved an object for kernel space usage.
>>
>> Userspace, though, needs to know the full address range.
>>
>> Fixes: 9bb66c179f50 ("drm/i915: Reserve some kernel space per vm")
>> Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
>> Cc: Andrzej Hajda <andrzej.hajda@intel.com>
>> Cc: Chris Wilson <chris.p.wilson@linux.intel.com>
>> Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
>> Cc: Michal Mrozek <michal.mrozek@intel.com>
>> Cc: Nirmoy Das <nirmoy.das@intel.com>
>> Cc: <stable@vger.kernel.org> # v6.2+
>> ---
>>   drivers/gpu/drm/i915/gt/gen8_ppgtt.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c 
>> b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
>> index fa46d2308b0e..d76831f50106 100644
>> --- a/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
>> +++ b/drivers/gpu/drm/i915/gt/gen8_ppgtt.c
>> @@ -982,8 +982,9 @@ static int gen8_init_rsvd(struct 
>> i915_address_space *vm)
>>         vm->rsvd.vma = i915_vma_make_unshrinkable(vma);
>>       vm->rsvd.obj = obj;
>> -    vm->total -= vma->node.size;
>> +
>>       return 0;
>> +
>>   unref:
>>       i915_gem_object_put(obj);
>>       return ret;
>
>