Re: [Xen-devel] [PATCH v2 1/1] tools: Handle xc_maxmem adjustments

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 15/04/15 10:57, Stefano Stabellini wrote:
> On Wed, 15 Apr 2015, Andrew Cooper wrote:
>> On 14/04/15 23:06, Don Slutz wrote:
>>> This fixes an issue where "xl save" followed by "xl restore" reports:
>>> "xc: error: Failed to allocate memory for batch.!: Internal error"
>>>
>>> One of the ways to get into this state is to have more then 4 e1000
>>> nics configured.
>>>
>>> Signed-off-by: Don Slutz <dslutz@xxxxxxxxxxx>
>> I still don't think this is the correct solution, although I will
>> concede that this is a far better patch than v1.
>>
>> Going back to the original problem, why does Qemu need to change maxmem
>> in the first place?  You talk about e1000 option roms, but the option
>> roms themselves must be allocated in an appropriate PCI bridge window.
> QEMU allocates actual memory to store the option roms using
> xc_domain_populate_physmap_exact, increasing the total amount of ram
> allocated to the guest. QEMU needs to increase maxmem too, otherwise
> memory allocations will fail after a few option roms.

It doesn't need to.  The domain already has that much ram allocated to
itself and otherwise wasted.  Qemu should reuse that ram rather than
wasting more.

~Andrew

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