linux-kernel - Re: [PATCH] drm/ttm: provide default page protection for UML

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Date:   Wed, 1 Sep 2021 22:52:38 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        linux-kernel@...r.kernel.org
Cc:     Thomas Hellström 
        <thomas.hellstrom@...ux.intel.com>,
        Christian König <christian.koenig@....com>,
        Huang Rui <ray.huang@....com>, dri-devel@...ts.freedesktop.org,
        Jeff Dike <jdike@...toit.com>,
        Richard Weinberger <richard@....at>,
        linux-um@...ts.infradead.org, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH] drm/ttm: provide default page protection for UML

On 9/1/21 10:48 PM, Anton Ivanov wrote:
> On 02/09/2021 03:01, Randy Dunlap wrote:
>> boot_cpu_data [struct cpuinfo_um (on UML)] does not have a struct
>> member named 'x86', so provide a default page protection mode
>> for CONFIG_UML.
>>
>> Mends this build error:
>> ../drivers/gpu/drm/ttm/ttm_module.c: In function ‘ttm_prot_from_caching’:
>> ../drivers/gpu/drm/ttm/ttm_module.c:59:24: error: ‘struct cpuinfo_um’ has no member named ‘x86’
>>    else if (boot_cpu_data.x86 > 3)
>>                          ^
>>
>> Fixes: 3bf3710e3718 ("drm/ttm: Add a generic TTM memcpy move for page-based iomem")
>> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
>> Cc: Thomas Hellström <thomas.hellstrom@...ux.intel.com>
>> Cc: Christian König <christian.koenig@....com>
>> Cc: Huang Rui <ray.huang@....com>
>> Cc: dri-devel@...ts.freedesktop.org
>> Cc: Jeff Dike <jdike@...toit.com>
>> Cc: Richard Weinberger <richard@....at>
>> Cc: Anton Ivanov <anton.ivanov@...bridgegreys.com>
>> Cc: linux-um@...ts.infradead.org
>> Cc: David Airlie <airlied@...ux.ie>
>> Cc: Daniel Vetter <daniel@...ll.ch>
>> ---
>>   drivers/gpu/drm/ttm/ttm_module.c |    4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> --- linux-next-20210901.orig/drivers/gpu/drm/ttm/ttm_module.c
>> +++ linux-next-20210901/drivers/gpu/drm/ttm/ttm_module.c
>> @@ -53,6 +53,9 @@ pgprot_t ttm_prot_from_caching(enum ttm_
>>       if (caching == ttm_cached)
>>           return tmp;
>> +#ifdef CONFIG_UML
>> +    tmp = pgprot_noncached(tmp);
>> +#else
>>   #if defined(__i386__) || defined(__x86_64__)
>>       if (caching == ttm_write_combined)
>>           tmp = pgprot_writecombine(tmp);
>> @@ -69,6 +72,7 @@ pgprot_t ttm_prot_from_caching(enum ttm_
>>   #if defined(__sparc__)
>>       tmp = pgprot_noncached(tmp);
>>   #endif
>> +#endif
>>       return tmp;
>>   }
> 
> Patch looks OK.
> 
> I have a question though - why all of DRM is not !UML in config. Not like we can use them.

I have no idea about that.
Hopefully one of the (other) UML maintainers can answer you.

thanks.
-- 
~Randy