linux-kernel - Re: [PATCH 5/5] drm/xe/query: use PAGE

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Message-ID: <c9eb3743-cd41-4ef6-bb8b-19d049edc312@aosc.io>
Date: Wed, 26 Feb 2025 15:27:24 +0800
From: Mingcong Bai <jeffbai@...c.io>
To: Matthew Brost <matthew.brost@...el.com>
Cc: Lucas De Marchi <lucas.demarchi@...el.com>,
 Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
 Rodrigo Vivi <rodrigo.vivi@...el.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 José Roberto de Souza <jose.souza@...el.com>,
 Francois Dugast <francois.dugast@...el.com>,
 Alan Previn <alan.previn.teres.alexis@...el.com>,
 Zhanjun Dong <zhanjun.dong@...el.com>, Matt Roper
 <matthew.d.roper@...el.com>, Mateusz Naklicki <mateusz.naklicki@...el.com>,
 Mauro Carvalho Chehab <mauro.chehab@...ux.intel.com>,
 Zbigniew Kempczyński <zbigniew.kempczynski@...el.com>,
 intel-xe@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, Kexy Biscuit <kexybiscuit@...c.io>,
 Shang Yatsen <429839446@...com>, stable@...r.kernel.org,
 Haien Liang <27873200@...com>, Shirong Liu <lsr1024@...com>,
 Haofeng Wu <s2600cw2@....com>
Subject: Re: [PATCH 5/5] drm/xe/query: use PAGE_SIZE as the minimum page
 alignment



在 2025/2/26 12:43, Matthew Brost 写道:
> On Wed, Feb 26, 2025 at 10:00:22AM +0800, Mingcong Bai via B4 Relay wrote:
>> From: Mingcong Bai <jeffbai@...c.io>
>>
>> As this component hooks into userspace API, it should be assumed that it
>> will play well with non-4K/64K pages.
>>
>> Use `PAGE_SIZE' as the final reference for page alignment instead.
>>
>> Cc: stable@...r.kernel.org
>> Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
>> Fixes: 801989b08aff ("drm/xe/uapi: Make constant comments visible in kernel doc")
>> Tested-by: Mingcong Bai <jeffbai@...c.io>
>> Tested-by: Haien Liang <27873200@...com>
>> Tested-by: Shirong Liu <lsr1024@...com>
>> Tested-by: Haofeng Wu <s2600cw2@....com>
>> Link: https://github.com/FanFansfan/loongson-linux/commit/22c55ab3931c32410a077b3ddb6dca3f28223360
>> Co-developed-by: Shang Yatsen <429839446@...com>
>> Signed-off-by: Shang Yatsen <429839446@...com>
>> Signed-off-by: Mingcong Bai <jeffbai@...c.io>
>> ---
>>   drivers/gpu/drm/xe/xe_query.c | 2 +-
>>   include/uapi/drm/xe_drm.h     | 2 +-
>>   2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_query.c b/drivers/gpu/drm/xe/xe_query.c
>> index c059639613f7b548c168f808b7b7b354f1cf3c94..8a017c526942d1f2b401e8b9a4244e6083d7b1e5 100644
>> --- a/drivers/gpu/drm/xe/xe_query.c
>> +++ b/drivers/gpu/drm/xe/xe_query.c
>> @@ -336,7 +336,7 @@ static int query_config(struct xe_device *xe, struct drm_xe_device_query *query)
>>   		config->info[DRM_XE_QUERY_CONFIG_FLAGS] =
>>   			DRM_XE_QUERY_CONFIG_FLAG_HAS_VRAM;
>>   	config->info[DRM_XE_QUERY_CONFIG_MIN_ALIGNMENT] =
>> -		xe->info.vram_flags & XE_VRAM_FLAGS_NEED64K ? SZ_64K : SZ_4K;
>> +		xe->info.vram_flags & XE_VRAM_FLAGS_NEED64K ? SZ_64K : PAGE_SIZE;
> 
> We should probably assert or build a bug somewhere to ensure SZ_64K >=
> PAGE_SIZE for future-proofing. Otherwise, I think the patch makes sense.
> One more comment below.

Hmm, >= 64KiB kernel pages don't seem to be a thing yet but this does 
make sense for the sake of completeness. Will change in v2.

> 
>>   	config->info[DRM_XE_QUERY_CONFIG_VA_BITS] = xe->info.va_bits;
>>   	config->info[DRM_XE_QUERY_CONFIG_MAX_EXEC_QUEUE_PRIORITY] =
>>   		xe_exec_queue_device_get_max_priority(xe);
>> diff --git a/include/uapi/drm/xe_drm.h b/include/uapi/drm/xe_drm.h
>> index f62689ca861a4673b885629460c11d6f3bc6523d..db7cf904926ebd6789a29d620161ac051e59f13f 100644
>> --- a/include/uapi/drm/xe_drm.h
>> +++ b/include/uapi/drm/xe_drm.h
>> @@ -394,7 +394,7 @@ struct drm_xe_query_mem_regions {
>>    *    - %DRM_XE_QUERY_CONFIG_FLAG_HAS_VRAM - Flag is set if the device
>>    *      has usable VRAM
>>    *  - %DRM_XE_QUERY_CONFIG_MIN_ALIGNMENT - Minimal memory alignment
>> - *    required by this device, typically SZ_4K or SZ_64K
>> + *    required by this device, typically PAGE_SIZE.
> 
> So I think the kernel doc needs bit more updating here, how about:
> 
> Minimal memory alignment required by this device and the CPU. The
> minimum page size for the device is usually SZ_4K or SZ_64K, while for
> the CPU, it is PAGE_SIZE. This value is calculated by
> max(min_gpu_page_size, PAGE_SIZE). This alignment is enforced on
> buffer object allocations and VM binds.
> 
> Again welcome others CC'd suggestion on this updated kernel doc.

Looks good to me, will revise in v2.

Best Regards,
Mingcong Bai

> 
> Matt
> 
>>    *  - %DRM_XE_QUERY_CONFIG_VA_BITS - Maximum bits of a virtual address
>>    *  - %DRM_XE_QUERY_CONFIG_MAX_EXEC_QUEUE_PRIORITY - Value of the highest
>>    *    available exec queue priority
>>
>> -- 
>> 2.48.1
>>
>>