Re: [libvirt] [PATCH 3/5] qemu: prefer memfd for anonymous memory

Hi On Tue, Sep 11, 2018 at 2:46 AM, John Ferlan <jferlan(a)redhat.com&gt; wrote: > > On 09/07/2018 07:32 AM, marcandre.lureau(a)redhat.com wrote: >> From: Marc-André Lureau <marcandre.lureau(a)redhat.com&gt; >> > > Would be nice to have a few more words here. If you provide them I can > add them... The if statement is difficult to read unless you know what > each field really means. hostmem-memfd is quite similar to hostmem-file. The main benefits are that it doesn't need to create filesystem files, and it also enforces sealing, providing a bit more safety. > secondary question - should we document what gets used?, e.g.: > > https://libvirt.org/formatdomain.html#elementsMemoryBacking > > Seems to me the preference to use memfd is for memory backing using > anonymous source for nvdimm's without a defined path, but sometimes my > wording doesn't match reality. Yes it could be documented. But it's now an allocation decision that could evolve, or an implementation detail. Would you like to see something like that? <dt><code>source</code></dt> - <dd>In this attribute you can switch to file memorybacking or keep - default anonymous.</dd> + <dd>In this attribute you can switch to file memorybacking or + keep default anonymous. <span class="since">Since 4.8.0</span>, + when the memory is anonymous and the host supports it, libvirt + will use a memfd memory backing, providing additional safety + guarantees. + </dd> <dt><code>access</code></dt>