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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

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.

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