linux-kernel - Re: [PATCH] xen/balloon: Mark unallocated host memory as UNUSABLE

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Date:   Fri, 15 Dec 2017 15:47:19 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xen.org, linux-kernel@...r.kernel.org
Cc:     helgaas@...nel.org, christian.koenig@....com
Subject: Re: [PATCH] xen/balloon: Mark unallocated host memory as UNUSABLE

On 15/12/17 15:24, Boris Ostrovsky wrote:
> 
>>> +
>>> +	hostmem_resource->start = max_addr;
>>> +	hostmem_resource->end = entry->addr + entry->size;
>>> +	for (; i < memmap.nr_entries; i++) {
>>> +		entry = &xen_e820_table->entries[i];
>>> +		if (entry->type == E820_TYPE_RAM)
>> Shouldn't that be != ?
> 
> No, the idea here is to populate hostmem_resource with ranges already
> taken by things other than RAM, leaving memory regions as available for
> the balloon hotplug. This will allow us to use allocate_resource(),
> which searches for a free range, in the balloon driver.

But why says the comment "Host memory not allocated to dom0" then?
And why are you trying to allocate from this resource in case of
hotplugging memory (and fall back to iomem_resource in case of
failure)?

Either the comment is completely wrong and I don't understand the
logic here, or your code is wrong.


Juergen