The code to align ppc64 NVDIMMs on post parse was introduced in
commit d3f3c2c97f. That commit failed to realize that we
can't align memory unconditionally. As of commit c7d7ba85a6
("qemu: command: Align memory sizes only on fresh starts"),
all memory alignment should be executed only when we're not
migrating or in a snapshot.
This revert does not break any guests in the wild, given that
ppc64 NVDIMMs are still being aligned in qemuDomainAlignMemorySizes().
Next patch will introduce a mechanism where we can have post
parse NVDIMM alignment for pSeries without breaking the
intended design, as defined by c7d7ba85a6.
This reverts commit d3f3c2c97f.
Reviewed-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
We can leave out things like USB controller, memballoon device,
kernel and initrd since they're not the focus of the tests.
Propagating some information from the output files back to the
input files makes it easier to compare them, as it reduces the
resulting diff, and in the case of the qemuxml2xml test for
memory-hotplug-ppc64-nonuma it allows us to convert the output
file into a symlink, since in the specific case the XML doesn't
change at all.
Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
The alignment for the pSeries NVDIMM does not depend on runtime
constraints. This means that it can be done in device parse
time, instead of runtime, allowing the domain XML to reflect
what the auto-alignment would do when the domain starts.
This brings consistency between the NVDIMM size reported by the
domain XML and what the guest sees, without impacting existing
guests that are using an unaligned size - they'll work as usual,
but the domain XML will be updated with the actual size of the
NVDIMM.
Reviewed-by: Andrea Bolognani <abologna@redhat.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
In [1], changes were made to remove the existing auto-alignment
for pSeries NVDIMM devices. That design promotes strange situations
where the NVDIMM size reported in the domain XML is different
from what QEMU is actually using. We removed the auto-alignment
and relied on standard size validation.
However, this goes against Libvirt design philosophy of not
tampering with existing guest behavior, as pointed out by Daniel
in [2]. Since we can't know for sure whether there are guests that
are relying on the auto-alignment feature to work, the changes
made in [1] are a direct violation of this rule.
This patch reverts [1] entirely, re-enabling auto-alignment for
pSeries NVDIMM as it was before. Changes will be made to ease
the limitations of this design without hurting existing
guests.
This reverts the following commits:
- commit 2d93cbdea9
Revert "formatdomain.html.in: mention pSeries NVDIMM 'align down' mechanic"
- commit 0ee56369c8
qemu_domain.c: change qemuDomainMemoryDeviceAlignSize() return type
- commit 07de813924
qemu_domain.c: do not auto-align ppc64 NVDIMMs
- commit 0ccceaa57c
qemu_validate.c: add pSeries NVDIMM size alignment validation
- commit 4fa2202d88
qemu_domain.c: make qemuDomainGetMemorySizeAlignment() public
[1] https://www.redhat.com/archives/libvir-list/2020-July/msg02010.html
[2] https://www.redhat.com/archives/libvir-list/2020-September/msg00572.html
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>
The existing auto-align behavior for pSeries has the idea to
alleviate user configuration of the NVDIMM size, given that the
alignment calculation is not trivial to do (256MiB alignment
of mem->size - mem->label_size value, a.k.a guest area). We
align mem->size down to avoid end of file problems.
The end result is not ideal though. We do not touch the domain
XML, meaning that the XML can report a NVDIMM size 255MiB smaller
than the actual size the guest is seeing. It also adds one more
thing to consider in case the guest is reporting less memory
than declared, since the auto-align is transparent to the
user.
Following Andrea's suggestion in [1], let's instead do an
size alignment validation. If the NVDIMM is unaligned, error out
and suggest a rounded up value. This can be bothersome to users,
but will bring consistency of NVDIMM size between the domain XML
and the guest.
This approach will force existing non-running pSeries guests to
readjust the NVDIMM value in their XMLs, if necessary. No changes
were made for x86 NVDIMM support.
[1] https://www.redhat.com/archives/libvir-list/2020-July/msg01471.html
Suggested-by: Andrea Bolognani <abologna@redhat.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Using the 'uuid' element for ppc64 NVDIMM memory added in the
previous patch, use it in qemuBuildMemoryDeviceStr() to pass
it over to QEMU.
Another ppc64 restriction is the necessity of a mem->labelsize,
given than ppc64 only support label-area backed NVDIMMs.
Finally, we don't want ppc64 NVDIMMs to align up due to the
high risk of going beyond the end of file with a 256MiB
increment that the user didn't predict. Align it down
instead. If target size is less than the minimum of
256MiB + labelsize, error out since QEMU will error out
if we attempt to round it up to the minimum.
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
ppc64 NVDIMM support was implemented in QEMU by commit [1].
The support is similar to what x86 already does, aside from
an extra 'uuid' element.
This patch introduces a new optional 'uuid' element for the
NVDIMM memory model. This element behaves like the 'uuid'
element of the domain definition - if absent, we'll create
a new one, otherwise use the one provided by the XML.
The 'uuid' element is exclusive to pseries guests and are
unavailable for other architectures.
Next patch will use this new element to add NVDIMM support
for ppc64.
[1] ee3a71e366
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
