linux-kernel - Re: [PATCH 18/22] mm: mark DEVICE

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Message-ID: <a27251ad-a152-f84d-139d-e1a3bf01c153@nvidia.com>
Date:   Thu, 13 Jun 2019 12:53:02 -0700
From:   Ralph Campbell <rcampbell@...dia.com>
To:     Jason Gunthorpe <jgg@...lanox.com>, Christoph Hellwig <hch@....de>
CC:     Dan Williams <dan.j.williams@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Ben Skeggs <bskeggs@...hat.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 18/22] mm: mark DEVICE_PUBLIC as broken


On 6/13/19 12:44 PM, Jason Gunthorpe wrote:
> On Thu, Jun 13, 2019 at 11:43:21AM +0200, Christoph Hellwig wrote:
>> The code hasn't been used since it was added to the tree, and doesn't
>> appear to actually be usable.  Mark it as BROKEN until either a user
>> comes along or we finally give up on it.
>>
>> Signed-off-by: Christoph Hellwig <hch@....de>
>>   mm/Kconfig | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/mm/Kconfig b/mm/Kconfig
>> index 0d2ba7e1f43e..406fa45e9ecc 100644
>> +++ b/mm/Kconfig
>> @@ -721,6 +721,7 @@ config DEVICE_PRIVATE
>>   config DEVICE_PUBLIC
>>   	bool "Addressable device memory (like GPU memory)"
>>   	depends on ARCH_HAS_HMM
>> +	depends on BROKEN
>>   	select HMM
>>   	select DEV_PAGEMAP_OPS
> 
> This seems a bit harsh, we do have another kconfig that selects this
> one today:
> 
> config DRM_NOUVEAU_SVM
>          bool "(EXPERIMENTAL) Enable SVM (Shared Virtual Memory) support"
>          depends on ARCH_HAS_HMM
>          depends on DRM_NOUVEAU
>          depends on STAGING
>          select HMM_MIRROR
>          select DEVICE_PRIVATE
>          default n
>          help
>            Say Y here if you want to enable experimental support for
>            Shared Virtual Memory (SVM).
> 
> Maybe it should be depends on STAGING not broken?
> 
> or maybe nouveau_svm doesn't actually need DEVICE_PRIVATE?
> 
> Jason

I think you are confusing DEVICE_PRIVATE for DEVICE_PUBLIC.
DRM_NOUVEAU_SVM does use DEVICE_PRIVATE but not DEVICE_PUBLIC.