Re: [PATCH for-4.12 v2 2/2] xen/arm: Stop relocating Xen

[Julien Grall <julien.grall@arm.com>]

On 12/18/18 12:09 PM, Andrii Anisov wrote:
> Hello Julien,

Hi,

> On 17.12.18 19:34, Andrii Anisov wrote:
>> I see something like following as a quick WA (not even build tested):
>>
>> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
>> index d2c63a8..bf72ba9 100644
>> --- a/xen/arch/arm/domain_build.c
>> +++ b/xen/arch/arm/domain_build.c
>> @@ -223,8 +223,9 @@ fail:
>>    * meet these requirements directly. So instead of proceed as follows:
>>    *
>>    * We first allocate the largest allocation we can as low as we
>> - * can. This then becomes the first bank. This bank must be at least
>> - * 128MB (or dom0_mem if that is smaller).
>> + * can. This then becomes the first bank. This bank is at least 128MB 
>> even if
>> + * dom0 is configured for less. It is the way to get that bank 128MB 
>> aligned,
>> + * what is required for 32-bit zImage.
>>    *
>>    * Then we start allocating more memory, trying to allocate the
>>    * largest possible size and trying smaller sizes until we
>> @@ -253,7 +254,7 @@ static void __init allocate_memory_11(struct 
>> domain *d,
>>                                         struct kernel_info *kinfo)
>>   {
>>       const unsigned int min_low_order =
>> -        get_order_from_bytes(min_t(paddr_t, dom0_mem, MB(128)));
>> +        get_order_from_bytes(MB(128));
>>       const unsigned int min_order = get_order_from_bytes(MB(4));
>>       struct page_info *pg;
>>       unsigned int order = get_allocation_size(kinfo->unassigned_mem);
>> @@ -268,6 +269,10 @@ static void __init allocate_memory_11(struct 
>> domain *d,
>>        */
>>       BUG_ON(!is_domain_direct_mapped(d));
>>
>> +    if ( dom0_mem < MB(128))
>> +        printk(XENLOG_WARNING "Allocating 128MB for Domain0 with 
>> %"PRIu64"MB\n",
>> +               dom0_mem/MB(1));
>> +
>>       printk("Allocating 1:1 mappings totalling %ldMB for dom0:\n",
>>              /* Don't want format this as PRIpaddr (16 digit hex) */
>>              (unsigned long)(kinfo->unassigned_mem >> 20));
>>
>>
>> But I'm not sure if it worth to be sent, because I'm going to rewrite 
>> it soon.
> 
>  From the second thought, we have last posting date for 4.12 already in 
> the past. So redesign will not go to 4.12.
> Maybe it worth to have the thing above as a bugfix for 4.12?
> What do you think?

AFAICT, it was possible to boot a Dom0 with only 64MB on Arm64. So I am 
not entirely why we would also limit the size there.

For Arm32, I think we should just return an error and fail the domain 
build. If you ask 64MB and we give you 128MB then something is already 
really wrong.

Anyway, I think this should be submitted properly to discuss for Xen 
4.12 inclusion.

Cheers,

-- 
Julien Grall

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