On 29.04.22 16:52, Anthony PERARD wrote:
> On Wed, Apr 20, 2022 at 10:04:26AM +0200, Juergen Gross wrote:
>> libxl_domain_setmaxmem() called during "xl mem-max" should update the
>> domain's memory/static-max Xenstore node, as otherwise "xl mem-set"
>> won't be able to set the memory size to the new maximum.
> 
> Setting domain's memory higher than the original mem-max only works on
> PV and maybe PVH guest, right? Because on HVM, QEMU is told about
> maxmem when starting a guest, and allocates some stuff from this address
> (vga buffer, pci rom I think) so trying to give HVM guest more memory
> after the fact is probably not going to go smoothly.

Works without a problem.

This area is marked in the e820 memory map, so the guest won't use it to
add memory.

> 
>> Adjust the related comments and documentation accordingly.
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> ---
>> V2:
>> - adjust comments and docs (Anthony Perard)
> 
> Maybe `man xl` should be updated as well. In the section about `xl
> mem-max`, there is:
>      "Note however that the initial maxmem value is still used as an
>      upper limit for xl mem-set.  Also note that calling xl mem-set will
>      reset this value."
> 
> That wouldn't be true anymore with this patch.

Weird. I did modify that man page, but obviously didn't check it was
really added to the patch. Sorry for that, will resend the patch with
that change included.


Juergen