Re: [Xen-devel] [PATCH v6 12/22] arm/acpi: Prepare EFI memory descriptor for Dom0

[Shannon Zhao <shannon.zhao@xxxxxxxxxx>]

On 2016年03月23日 00:04, Julien Grall wrote:
> Hi Shannon,
> 
> On 22/03/16 13:16, Shannon Zhao wrote:
>> On 2016年03月22日 00:51, Julien Grall wrote:
>>>> +        memory_map[offset].Attribute = EFI_MEMORY_WB;
>>>> +    }
>>>> +
>>>> +    for( i = 0; i < acpi_mem.nr_banks; i++, offset++ )
>>>> +    {
>>>> +        memory_map[offset].Type = EfiACPIReclaimMemory;
>>>> +        memory_map[offset].PhysicalStart = acpi_mem.bank[i].start;
>>>> +        memory_map[offset].NumberOfPages =
>>>> PFN_UP(acpi_mem.bank[i].size);
>>>
>>> Ditto
>>>
>>> You are also assuming that acpi_mem.bank[i].size will always be aligned
>>> to 4KB. If so, we may expose unwanted data to the guest.
>>>
>>> Based on how the field is set, I would add a BUG_ON to ensure this
>>> condition.
>> UEFI spec says
>> "EFI memory descriptors of type EfiACPIReclaimMemory and
>> EfiACPIMemoryNVS must be aligned on a 4 KiB boundary and must be a
>> multiple of 4 KiB in size."
>>
>> So I think the size is aligned to 4kb, right?
> 
> Right. I was suggested to add a BUG_ON to document the constraint and
> ensure nobody will play with acpi_mem outside EFI.
> 
> A such check would also be nice for mem->bank[i].size;
sorry, I didn't get the idea. How to add a BUG_ON to check the size?

Thanks,
-- 
Shannon

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel