Re: [PATCH] drm/xe: put COMMON_SLICE_CHICKEN3 on the allowlist for UMD

[Lionel Landwerlin <lionel.g.landwerlin@intel.com>]

On 05/01/2026 20:54, Gustavo Sousa wrote:
> Quoting Lionel Landwerlin (2026-01-05 12:02:22-03:00)
>> Similar to i915's commit cebc13de7e704b1355bea208a9f9cdb042c74588
>> ("drm/i915: Whitelist COMMON_SLICE_CHICKEN3 for UMD access")
>>
>> A recommended tuning setting for both gen12 and Xe_HP platforms
>> requires that we grant userspace r/w access to the
>> COMMON_SLICE_CHICKEN3 register.
>>
>> Bspec: 73993, 73994, 31870, 68331
>> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
>> ---
>> drivers/gpu/drm/xe/xe_reg_whitelist.c | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_reg_whitelist.c b/drivers/gpu/drm/xe/xe_reg_whitelist.c
>> index 1391cb6ec9c62..4dcbc42574bf5 100644
>> --- a/drivers/gpu/drm/xe/xe_reg_whitelist.c
>> +++ b/drivers/gpu/drm/xe/xe_reg_whitelist.c
>> @@ -45,6 +45,11 @@ static const struct xe_rtp_entry_sr register_whitelist[] = {
>>            XE_RTP_RULES(GRAPHICS_VERSION_RANGE(1200, 1210), ENGINE_CLASS(RENDER)),
>>            XE_RTP_ACTIONS(WHITELIST(COMMON_SLICE_CHICKEN1, 0))
>>          },
>> +        { XE_RTP_NAME("allow_common_slice_chicken3"),
>> +          XE_RTP_RULES(GRAPHICS_VERSION_RANGE(1200, XE_RTP_END_VERSION_UNDEFINED),
> With XE_RTP_END_VERSION_UNDEFINED, this spans to any current and future
> GT containig graphics version 12 or higher.  I believe we need to limit
> this to 12.74.
>
> --
> Gustavo Sousa


The problem is that UMD still wants to enable this performance feature 
from this register.

On Windows there is a way for the UMD to request the programming of the 
bit without the allowlist on Xe2+.

But there is no such mechanism on Linux.


-Lionel


>
>> +                       ENGINE_CLASS(RENDER)),
>> +          XE_RTP_ACTIONS(WHITELIST(COMMON_SLICE_CHICKEN3, 0))
>> +        },
>>          { XE_RTP_NAME("1806527549"),
>>            XE_RTP_RULES(GRAPHICS_VERSION_RANGE(1200, 1210), ENGINE_CLASS(RENDER)),
>>            XE_RTP_ACTIONS(WHITELIST(HIZ_CHICKEN, 0))
>> -- 
>> 2.43.0
>>