| Message ID | 20210520133611.39540-1-andrea.righi@canonical.com |
|---|---|
| Headers | show |
| Series | kvm: properly tear down PV features on hibernate | expand |
BugLink: https://bugs.launchpad.net/bugs/1920944 On Thu, May 20, 2021 at 03:36:06PM +0200, Andrea Righi wrote: > [Impact] > > In LP: #1918694 we applied a fix and a workaround to solve the > hibernation issues on c5.18xlarge. The workaround was in the form of a > SAUCE patch: > > "UBUNTU: SAUCE: aws: kvm: double the size of hv_clock_boot" > > It looks like we can replace this workaround with a proper fix, by > applying this patch: > > http://next.patchew.org/Linux/20210414123544.1060604-1-vkuznets@redhat.com/ > > This is required because various PV features (Async PF, PV EOI, steal > time) work through memory shared with hypervisor and when we restore > from hibernation we must properly tear down all these features to make > sure hypervisor doesn't write to stale locations after we jump to the > previously hibernated kernel. > > For this reason it is safe to apply this patch set also to the all the > generic kernels and not just AWS. > > [Test plan] > > This can be easily tested on AWS (but it should be reproduced by > hibernating any kvm instance with multiple CPUs). Create a c5.18xlarge > instance, run the memory stress test script (the same test script that > we are using to stress test hibernation), trigger the hibernate event, > trigger the resume event. Repeat a couple of times and the problem is > very likely to happen. > > [Fix] > > On the AWS kernel replace "UBUNTU: SAUCE: aws: kvm: double the size of > hv_clock_boot" with: > > http://next.patchew.org/Linux/20210414123544.1060604-1-vkuznets@redhat.com/ > > For the other kernels, simply apply this patch set. > > The fix has been tested extensively in the AWS infrastructure with > positive results. > > [Regression potential] > > This new code introduced by the fix can be executed also when a CPU is > put offline, so we may see potential regressions in the KVM CPU > hot-plugging.
On 20/05/2021 10:36, Andrea Righi wrote: > [Impact] > > In LP: #1918694 we applied a fix and a workaround to solve the > hibernation issues on c5.18xlarge. The workaround was in the form of a > SAUCE patch: > > "UBUNTU: SAUCE: aws: kvm: double the size of hv_clock_boot" > > It looks like we can replace this workaround with a proper fix, by > applying this patch: > > http://next.patchew.org/Linux/20210414123544.1060604-1-vkuznets@redhat.com/ > > This is required because various PV features (Async PF, PV EOI, steal > time) work through memory shared with hypervisor and when we restore > from hibernation we must properly tear down all these features to make > sure hypervisor doesn't write to stale locations after we jump to the > previously hibernated kernel. > > For this reason it is safe to apply this patch set also to the all the > generic kernels and not just AWS. > > [Test plan] > > This can be easily tested on AWS (but it should be reproduced by > hibernating any kvm instance with multiple CPUs). Create a c5.18xlarge > instance, run the memory stress test script (the same test script that > we are using to stress test hibernation), trigger the hibernate event, > trigger the resume event. Repeat a couple of times and the problem is > very likely to happen. > > [Fix] > > On the AWS kernel replace "UBUNTU: SAUCE: aws: kvm: double the size of > hv_clock_boot" with: > > http://next.patchew.org/Linux/20210414123544.1060604-1-vkuznets@redhat.com/ > > For the other kernels, simply apply this patch set. > > The fix has been tested extensively in the AWS infrastructure with > positive results. > > [Regression potential] > > This new code introduced by the fix can be executed also when a CPU is > put offline, so we may see potential regressions in the KVM CPU > hot-plugging. > Thanks Andrea! LGTM: Acked-by: Guilherme G. Piccoli <gpiccoli@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com> From background chatter I gather this has been thoroughly tested. On 5/20/21 7:36 AM, Andrea Righi wrote: > [Impact] > > In LP: #1918694 we applied a fix and a workaround to solve the > hibernation issues on c5.18xlarge. The workaround was in the form of a > SAUCE patch: > > "UBUNTU: SAUCE: aws: kvm: double the size of hv_clock_boot" > > It looks like we can replace this workaround with a proper fix, by > applying this patch: > > http://next.patchew.org/Linux/20210414123544.1060604-1-vkuznets@redhat.com/ > > This is required because various PV features (Async PF, PV EOI, steal > time) work through memory shared with hypervisor and when we restore > from hibernation we must properly tear down all these features to make > sure hypervisor doesn't write to stale locations after we jump to the > previously hibernated kernel. > > For this reason it is safe to apply this patch set also to the all the > generic kernels and not just AWS. > > [Test plan] > > This can be easily tested on AWS (but it should be reproduced by > hibernating any kvm instance with multiple CPUs). Create a c5.18xlarge > instance, run the memory stress test script (the same test script that > we are using to stress test hibernation), trigger the hibernate event, > trigger the resume event. Repeat a couple of times and the problem is > very likely to happen. > > [Fix] > > On the AWS kernel replace "UBUNTU: SAUCE: aws: kvm: double the size of > hv_clock_boot" with: > > http://next.patchew.org/Linux/20210414123544.1060604-1-vkuznets@redhat.com/ > > For the other kernels, simply apply this patch set. > > The fix has been tested extensively in the AWS infrastructure with > positive results. > > [Regression potential] > > This new code introduced by the fix can be executed also when a CPU is > put offline, so we may see potential regressions in the KVM CPU > hot-plugging. > >