ACK/Cmnt: [SRU][F/aws][PATCH v3 0/6] aws: proper fix for c5.18xlarge hibernation issues

[Andrea Righi]

On Wed, May 19, 2021 at 12:23:22PM -0600, Tim Gardner wrote:
> Acked-by: Tim Gardner <tim.gardner at canonical.com>
> 
> pr_info() exists in focal/linux-aws. I'm curious why you didn't preserve it
> in patch 2/6 ?

Good point, I could have used pr_info(), but the original patch was
changing a pr_info() to another pr_info() and the original code has a
printk(), so I thought it was more consistent to keep the printk() and
change only the text like the original patch does...

-Andrea

> 
> On 5/19/21 9:15 AM, Andrea Righi wrote:
> > BugLink: https://bugs.launchpad.net/bugs/1920944
> > 
> > [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/
> > 
> > [Test plan]
> > 
> > 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]
> > 
> > Replace "UBUNTU: SAUCE: aws: kvm: double the size of hv_clock_boot"
> > with:
> > 
> > http://next.patchew.org/Linux/20210414123544.1060604-1-vkuznets@redhat.com/
> > 
> > The fix has been tested extensively in the AWS infrastructure with
> > positive results.
> > 
> > [Where problems could occur]
> > 
> > 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
> > hotplugging.
> > 
> > ----------------------------------------------------------------
> > Changelog (v2 -> v3):
> >   - updated backported / signed-off lines with the right upstream info
> >     (thanks Guilherme!)
> > 
> > NOTE: backport activity was minimal, it only required some context
> > adjustments to properly apply the changes.
> > 
> > Andrea Righi (1):
> >        Revert "UBUNTU: SAUCE: aws: kvm: double the size of hv_clock_boot"
> > 
> > Vitaly Kuznetsov (5):
> >        x86/kvm: Fix pr_info() for async PF setup/teardown
> >        x86/kvm: Teardown PV features on boot CPU as well
> >        x86/kvm: Disable kvmclock on all CPUs on shutdown
> >        x86/kvm: Disable all PV features on crash
> >        x86/kvm: Unify kvm_pv_guest_cpu_reboot() with kvm_guest_cpu_offline()
> > 
> >   arch/x86/include/asm/kvm_para.h |   9 ++----
> >   arch/x86/kernel/kvm.c           | 113 ++++++++++++++++++++++++++++++++++++++++++++----------------------
> >   arch/x86/kernel/kvmclock.c      |  28 ++---------------
> >   3 files changed, 79 insertions(+), 71 deletions(-)
> > 
> > 
> 
> -- 
> -----------
> Tim Gardner
> Canonical, Inc