Re: [v7][PATCH 07/16] hvmloader/e820: construct guest e820 table

["Chen, Tiejun" <tiejun.chen@intel.com>]

> I think I would say:
>
> --
> Now use the hypervisor-supplied memory map to build our final e820 table:
> * Add regions for BIOS ranges and other special mappings not in the
> hypervisor map
> * Add in the hypervisor regions
> * Adjust the lowmem and highmem regions if we've had to relocate
> memory (adding a highmem region if necessary)
> * Sort all the ranges so that they appear in memory order.
> --

I'll update this and thanks a lot.

>
>>
>> CC: Keir Fraser <keir@xen.org>
>> CC: Jan Beulich <jbeulich@suse.com>
>> CC: Andrew Cooper <andrew.cooper3@citrix.com>
>> CC: Ian Jackson <ian.jackson@eu.citrix.com>
>> CC: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
>> CC: Ian Campbell <ian.campbell@citrix.com>
>> CC: Wei Liu <wei.liu2@citrix.com>
>> Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
>> ---

[snip]

>> +    /* Low RAM goes here. Reserve space for special pages. */
>> +    BUG_ON(low_mem_end < (2u << 20));
>
> Won't this BUG if the guest was actually given less than 2GiB of RAM?

2u << 20 = 0x200000, so this is 2M, not 2G :)

>
>> +
>> +    /*
>> +     * We may need to adjust real lowmem end since we may
>> +     * populate RAM to get enough MMIO previously.
>> +     */

[snip]

>> +
>> +    /*
>> +     * And then we also need to adjust highmem.
>> +     */
>> +    if ( add_high_mem )
>> +    {
>> +        for ( i = 0; i < memory_map.nr_map; i++ )
>> +        {
>> +            if ( e820[i].type == E820_RAM &&
>> +                 e820[i].addr > (1ull << 32))
>> +                e820[i].size += add_high_mem;
>> +        }
>> +    }
>
> What if there was originally no high memory, but resizing the pci hole
> meant we had to create a high memory region?
>

You're right. We need to consider this case.

Thanks
Tiejun