On Thu, 2020-12-03 at 22:05 -0300, Daniel Henrique Barboza wrote: > qemuDomainAlignMemorySizes() has an operation order problem. We are > calculating 'initialmem' without aligning the memory modules first. > Since we're aligning the dimms afterwards this can create inconsistencies > in the end result. x86 has alignment of 1-2MiB and it's not severely > impacted by it, but pSeries works with 256MiB alignment and the difference > is noticeable. > > This is the case of the existing 'memory-hotplug-ppc64-nonuma' test. > The test consists of a 2GiB (aligned value) guest with 2 ~520MiB dimms, > both unaligned. 'initialmem' is calculated by taking total_mem and > subtracting the dimms size (via virDomainDefGetMemoryInitial()), which > wil give us 2GiB - 520MiB - 520MiB, ending up with a little more than > an 1GiB of 'initialmem'. Note that this value is now unaligned, and > will be aligned up via VIR_ROUND_UP(), and we'll end up with 'initialmem' > of 1GiB + 256MiB. Given that the dimms are aligned later on, the end > result for QEMU is that the guest will have a 'mem' size of 1310720k, > plus the two 512 MiB dimms, exceeding in 256MiB the desired 2GiB > memory and currentMemory specified in the XML. > > Existing guests can't be fixed without breaking ABI, but we have > code already in place to align pSeries NVDIMM modules for new guests. > Let's extend it to align all pSeries mem modules. > > A new test, 'memory-hotplug-ppc64-nonuma-abi-update', a copy of the > existing 'memory-hotplug-ppc64-nonuma', was added to demonstrate the > result for new pSeries guests. For the same unaligned XML mentioned > above, after applying this patch: > > - starting QEMU mem size without PARSE_ABI_UPDATE: > -m size=1310720k,slots=16,maxmem=4194304k \ (no changes) > > - starting QEMU mem size with PARSE_ABI_UPDATE: > -m size=1048576k,slots=16,maxmem=4194304k \ (size fixed) > > Reviewed-by: Michal Privoznik <mprivozn@xxxxxxxxxx> > Signed-off-by: Daniel Henrique Barboza <danielhb413@xxxxxxxxx> > --- > src/qemu/qemu_domain.c | 14 +++++-- > ...emory-hotplug-ppc64-nonuma-abi-update.args | 29 ++++++++++++++ > ...memory-hotplug-ppc64-nonuma-abi-update.xml | 1 + > tests/qemuxml2argvtest.c | 7 ++++ > ...memory-hotplug-ppc64-nonuma-abi-update.xml | 38 +++++++++++++++++++ > tests/qemuxml2xmltest.c | 7 ++++ > 6 files changed, 92 insertions(+), 4 deletions(-) > create mode 100644 tests/qemuxml2argvdata/memory-hotplug-ppc64-nonuma-abi-update.args > create mode 120000 tests/qemuxml2argvdata/memory-hotplug-ppc64-nonuma-abi-update.xml > create mode 100644 tests/qemuxml2xmloutdata/memory-hotplug-ppc64-nonuma-abi-update.xml Reviewed-by: Andrea Bolognani <abologna@xxxxxxxxxx> -- Andrea Bolognani / Red Hat / Virtualization
