Re: [Xen-devel] [PATCH]: Fix Xen domU boot with batched mprotect

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

>>> Jeremy Fitzhardinge <jeremy@xxxxxxxx> 17.10.08 17:19 >>>
>Jan Beulich wrote:
>>>>> Jeremy Fitzhardinge <jeremy@xxxxxxxx> 16.10.08 18:10 >>>
>>>>>         
>>> The current x86-64 implementation is:
>>>
>>> bool __virt_addr_valid(unsigned long x)
>>> {
>>>     if (x >= __START_KERNEL_map) {
>>>             x -= __START_KERNEL_map;
>>>             if (x >= KERNEL_IMAGE_SIZE)
>>>                     return false;
>>>     
>>
>> This, imo, is still broken (i.e. the name of the function still isn't matched
>> by the implementation): KERNEL_IMAGE_SIZE is a constant and doesn't
>> account for the fact that only the real kernel image can be relied upon
>> to be mapped.
>>   
>
>Perhaps, but I don't think it matters too much.  Unless you have a tiny 
>amount of physical memory, locations in the kernel mapping beyond the 
>actual kernel will still resolve to proper locations in the linear map.

Is e.g. 256Mb tiny? KERNEL_IMAGE_SIZE these days is 512Mb... Indeed,
when it was 40Mb (up until a few releases ago), this indeed wouldn't
matter.

Jan


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