Re: [PATCH for-4.14 2/3] xen/arm: Take into account the DMA width when allocating Dom0 memory banks

[Julien Grall <julien@xen.org>]

On 18/05/2020 21:34, Volodymyr Babchuk wrote:
> Hi Julien,

Hi Volodymyr,

Thank you for the review.

> 
> On Mon, 2020-05-18 at 12:30 +0100, Julien Grall wrote:
>> From: Julien Grall <jgrall@amazon.com>
>>
>> At the moment, Xen is assuming that all the devices are at least 32-bit
>> DMA capable. However, some SoCs have devices that may be able to access
>> a much restricted range. For instance, the Raspberry PI 4 has devices
>> that can only access the first GB of RAM.
>>
>> The function arch_get_dma_bit_size() will return the lowest DMA width on
>> the platform. Use it to decide what is the limit for the low memory.
>>
>> Signed-off-by: Julien GralL <jgrall@amazon.com>
>> ---
>>   xen/arch/arm/domain_build.c | 32 +++++++++++++++++++-------------
>>   1 file changed, 19 insertions(+), 13 deletions(-)
>>
>> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
>> index 430708753642..abc4e463d27c 100644
>> --- a/xen/arch/arm/domain_build.c
>> +++ b/xen/arch/arm/domain_build.c
>> @@ -211,10 +211,13 @@ fail:
>>    *    the ramdisk and DTB must be placed within a certain proximity of
>>    *    the kernel within RAM.
>>    * 3. For dom0 we want to place as much of the RAM as we reasonably can
>> - *    below 4GB, so that it can be used by non-LPAE enabled kernels (32-bit)
>> + *    below 4GB, so that it can be used by non-LPAE enabled kernels (32-bit).
> Is full stop really needed there?

I was meant to remove the line below as it is now part of 4). I will 
remove it in the next version.

Best regards,

-- 
Julien Grall