Re: [PATCH] drm/ttm: device address space != CPU address space

["Christian König" <deathsimple@vodafone.de>]

Even shifting doesn't help here. We have up to 48bits of physical 
address space on modern systems with still 4K page size.

This means 48-12=36bit address space, that won't fit into a 32bit 
integer no matter what.

Assuming we have already double checked drm_mm the patch is Reviewed-by: 
Christian König <christian.koenig@amd.com>

Regards,
Christian.

On 04.03.2015 09:01, Thomas Hellstrom wrote:
> Hi!
>
> IIRC, the interpretation of gpu_offset is fully controlled by the
> driver. That means to keep a native integer size
> you should be able to set
>
> radeon_gpu_offset := (ttm_gpu_offset << suitable_shift);
>
> However, if you feel that this is too intrusive in the driver, I'm not
> against the current patch as it stands. It's important, however that the
> interactions with drm_mm is sorted out. I'm not sure the patch that
> converted drm_mm to 64-bit instead
> of unsigned long went in. (There were similar arguments against that patch).
>
> Thanks,
> Thomas
>
>
> On 03/04/2015 06:18 AM, Alex Deucher wrote:
>> We need to store device offsets in 64 bit as the device
>> address space may be larger than the CPU's.
>>
>> Fixes GPU init failures on radeons with 4GB or more of
>> vram on 32 bit kernels.  We put vram at the start of the
>> GPU's address space so the gart aperture starts at 4 GB
>> causing all GPU addresses in the gart aperture to get
>> truncated.
>>
>> bug:
>> https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.freedesktop.org_show-5Fbug.cgi-3Fid-3D89072&d=AwIBAg&c=Sqcl0Ez6M0X8aeM67LKIiDJAXVeAw-YihVMNtXt-uEs&r=vpukPkBtpoNQp2IUKuFviOmPNYWVKmen3Jeeu55zmEA&m=M1rvbqZd6hlmRIsZmBXhSypX4cSQqZSddym13SRVKtg&s=sriG7bnxL46LbaYmq_FnswHY9WOrPvTbdK7um05zoxE&e=
>>
>> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
>> Cc: thellstrom@vmware.com
>> ---
>> Untested.  Someone more familiar with the ttm internals can
>> probably point out any additional bits I missed.  Heading to
>> bed now.
>>
>>   drivers/gpu/drm/ttm/ttm_bo.c    | 2 +-
>>   include/drm/ttm/ttm_bo_api.h    | 2 +-
>>   include/drm/ttm/ttm_bo_driver.h | 2 +-
>>   3 files changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
>> index d395b0b..8d9b7de 100644
>> --- a/drivers/gpu/drm/ttm/ttm_bo.c
>> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
>> @@ -74,7 +74,7 @@ static void ttm_mem_type_debug(struct ttm_bo_device *bdev, int mem_type)
>>   	pr_err("    has_type: %d\n", man->has_type);
>>   	pr_err("    use_type: %d\n", man->use_type);
>>   	pr_err("    flags: 0x%08X\n", man->flags);
>> -	pr_err("    gpu_offset: 0x%08lX\n", man->gpu_offset);
>> +	pr_err("    gpu_offset: 0x%08llX\n", man->gpu_offset);
>>   	pr_err("    size: %llu\n", man->size);
>>   	pr_err("    available_caching: 0x%08X\n", man->available_caching);
>>   	pr_err("    default_caching: 0x%08X\n", man->default_caching);
>> diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
>> index 0ccf7f2..c768ddf 100644
>> --- a/include/drm/ttm/ttm_bo_api.h
>> +++ b/include/drm/ttm/ttm_bo_api.h
>> @@ -249,7 +249,7 @@ struct ttm_buffer_object {
>>   	 * either of these locks held.
>>   	 */
>>   
>> -	unsigned long offset;
>> +	uint64_t offset; /* GPU address space is independent of CPU word size */
>>   	uint32_t cur_placement;
>>   
>>   	struct sg_table *sg;
>> diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h
>> index 142d752..813042c 100644
>> --- a/include/drm/ttm/ttm_bo_driver.h
>> +++ b/include/drm/ttm/ttm_bo_driver.h
>> @@ -277,7 +277,7 @@ struct ttm_mem_type_manager {
>>   	bool has_type;
>>   	bool use_type;
>>   	uint32_t flags;
>> -	unsigned long gpu_offset;
>> +	uint64_t gpu_offset; /* GPU address space is independent of CPU word size */
>>   	uint64_t size;
>>   	uint32_t available_caching;
>>   	uint32_t default_caching;
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