[PATCH] drm/ttm: Don't delete the system manager before the delayed delete

[Zack Rusin]

On 9/20/21 10:59 AM, Zack Rusin wrote:
>> On Sep 20, 2021, at 02:30, Christian König <christian.koenig at amd.com> wrote:
>>
>> Am 17.09.21 um 19:53 schrieb Zack Rusin:
>>> On some hardware, in particular in virtualized environments, the
>>> system memory can be shared with the "hardware". In those cases
>>> the BO's allocated through the ttm system manager might be
>>> busy during ttm_bo_put which results in them being scheduled
>>> for a delayed deletion.
>>
>> While the patch itself is probably fine the reasoning here is a clear NAK.
>>
>> Buffers in the system domain are not GPU accessible by definition, even in a shared environment and so *must* be idle.
> 
> I’m assuming that means they are not allowed to be ever fenced then, yes?

Any thoughts on this? I'd love a confirmation because it would mean I need to go and rewrite the vmwgfx_mob.c bits where we use TTM_PL_SYSTEM memory (through vmw_bo_create_and_populate) for a page table which is read by the host, and those bo's need to be fenced to prevent destruction of the page tables while the memory they point to is still used. So if those were never allowed to be fenced in the first place we probably need to add a new memory type to hold those page tables.

z