[Intel-gfx] [PATCH 3/3] drm/i915/bios: do not discard address space

[Lucas De Marchi]

On Fri, Nov 15, 2019 at 07:40:15PM +0200, Ville Syrjälä wrote:
>On Fri, Nov 08, 2019 at 01:13:53PM -0800, Lucas De Marchi wrote:
>> When we map the VBT through pci_map_rom() we may not be allowed
>> to simply discard the address space and go on reading the memory.
>> That doesn't work on my test system, but by dumping the rom via
>> sysfs I can can get the correct vbt. So change our find_vbt() to do
>> the same as done by pci_read_rom(), i.e. use memcpy_fromio().
>>
>> v2: the just the minimal changes by not bothering with the unaligned io
>> reads: this can be done on top (from Ville and Jani)
>>
>> Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>
>> ---
>>  drivers/gpu/drm/i915/display/intel_bios.c | 51 +++++++++++++++++------
>>  1 file changed, 39 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
>> index c79781e1ccbf..c079febae9c8 100644
>> --- a/drivers/gpu/drm/i915/display/intel_bios.c
>> +++ b/drivers/gpu/drm/i915/display/intel_bios.c
>> @@ -1811,28 +1811,52 @@ bool intel_bios_is_valid_vbt(const void *buf, size_t size)
>>  	return vbt;
>>  }
>>
>> -static const struct vbt_header *find_vbt(void __iomem *oprom, size_t size)
>> +static const struct vbt_header *copy_vbt(void __iomem *oprom, size_t size)

just noticed this shouldn't be const anymore, since the caller is
supposed to free the return

>>  {
>> +	void __iomem *p = NULL;
>> +	struct vbt_header *vbt;
>> +	u16 vbt_size;
>>  	size_t i;
>>
>>  	/* Scour memory looking for the VBT signature. */
>>  	for (i = 0; i + 4 < size; i++) {
>> -		void *vbt;
>> -
>>  		if (ioread32(oprom + i) != *((const u32 *)"$VBT"))
>>  			continue;
>>
>> -		/*
>> -		 * This is the one place where we explicitly discard the address
>> -		 * space (__iomem) of the BIOS/VBT.
>> -		 */
>> -		vbt = (void __force *)oprom + i;
>> -		if (intel_bios_is_valid_vbt(vbt, size - i))
>> -			return vbt;
>> -
>> +		p = oprom + i;
>> +		size -= i;
>>  		break;
>>  	}
>>
>> +	if (!p)
>> +		return NULL;
>> +
>> +	if (sizeof(struct vbt_header) > size) {
>> +		DRM_DEBUG_DRIVER("VBT header incomplete\n");
>> +		return NULL;
>> +	}
>> +
>> +	vbt_size = ioread16(p + offsetof(struct vbt_header, vbt_size));
>> +	if (vbt_size > size) {
>> +		DRM_DEBUG_DRIVER("VBT incomplete (vbt_size overflows)\n");
>> +		return NULL;
>> +	}
>> +
>> +	/* The rest will be validated by intel_bios_is_valid_vbt() */
>> +	vbt = kmalloc(vbt_size, GFP_KERNEL);
>> +	if (!vbt)
>> +		return NULL;
>> +
>> +	memcpy_fromio(vbt, p, vbt_size);
>> +
>> +	if (!intel_bios_is_valid_vbt(vbt, vbt_size))
>> +		goto err_free_vbt;
>> +
>> +	return vbt;
>> +
>> +err_free_vbt:
>> +	kfree(vbt);
>> +
>>  	return NULL;
>>  }
>>
>> @@ -1866,7 +1890,7 @@ void intel_bios_init(struct drm_i915_private *dev_priv)
>>  		if (!oprom)
>>  			goto out;
>>
>> -		vbt = find_vbt(oprom, size);
>> +		vbt = copy_vbt(oprom, size);
>>  		if (!vbt)
>>  			goto out;
>>
>> @@ -1902,6 +1926,9 @@ void intel_bios_init(struct drm_i915_private *dev_priv)
>>
>>  	if (oprom)
>>  		pci_unmap_rom(pdev, oprom);
>
>lgtm
>Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
>As a followup we could now move the rom map/unamp into copy_vbt() as
>there's no longer any need to keep it mapped across the whole thing.

yep, I will add this and a tentative to avoid the unaligned reads

thanks
Lucas De Marchi

>
>> +
>> +	if (vbt != dev_priv->opregion.vbt)
>> +		kfree(vbt);
>>  }
>>
>>  /**
>> --
>> 2.24.0
>
>-- 
>Ville Syrjälä
>Intel
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