On Tue, 13 Feb 2018 18:11:05 -0600 Michael Roth <mdr...@linux.vnet.ibm.com> wrote:
> This blog entry is intended as a follow-up to the original entry in > January regarding Spectre/Meltdown and the proposed changes to address > them in the upcoming 2.11.1 release. > > This entry is meant to accompany the 2.11.1 release (planned for > 2018-02-14) and document how to make use of the new options for > various architectures. > > Cc: Eduardo Habkost <ehabk...@redhat.com> > Cc: Paolo Bonzini <pbonz...@redhat.com> > Cc: Peter Maydell <peter.mayd...@linaro.org> > Cc: Suraj Jitindar Singh <sjitindarsi...@gmail.com> > Cc: David Gibson <da...@gibson.dropbear.id.au> > Cc: Christian Borntraeger <borntrae...@de.ibm.com> > Cc: Cornelia Huck <coh...@redhat.com> > Cc: Thomas Huth <th...@redhat.com> > Signed-off-by: Michael Roth <mdr...@linux.vnet.ibm.com> > --- > > The pseries/s390 bits have gotten some initial review (thanks > Suraj/Christian), > but it can definitely use some additional review on the x86 side of things. > > Also, Peter if think anything extra should to be mentioned on the ARM side > just > let me know what to add. > > .../2018-02-14-qemu-2-11-1-and-spectre-update.md | 180 > +++++++++++++++++++++ > 1 file changed, 180 insertions(+) > create mode 100644 _posts/2018-02-14-qemu-2-11-1-and-spectre-update.md [some comments/questions regarding s390 cpu models, adding DavidH on cc:] > +## enabling mitigations for s390 KVM guests > + > +For s390 guests there are 2 CPU options relating to Spectre/Meltdown: s/options/feature bits/ ? > + > +* bpb: Branch prediction blocking > +* ppa15: PPA15 is installed > + > +**bpb** requires a host kernel patched with: > + > + commit 35b3fde6203b932b2b1a5b53b3d8808abc9c4f60 > + KVM: s390: wire up bpb feature > + > +and both **bpb** and **ppa15** require a firmware with the appropriate > support > +level as well as guest kernel patches to enable the functionality within > +guests. Please check with your distro/vendor to confirm. > + > +Both **bpb** and **ppa15** are enabled by default with newer/patched host > +kernels, and can also be set manually. For example: > + > + qemu-system-s390x -M s390-ccw-virtio-2.11 ... \ > + -cpu zEC12,bpb=on,ppa15=on Do we also want to add that bpb/ppa15 are on if you use the _full_ model (as opposed to the _base_ model)? Or is this going into too much detail about the cpu model? > + > +WRT to migration, enabling **bpb** requires the source/target also have > **bpb** Either "WRT migration", or "With regard to migration" :) > +enabled. Since this is enabled by default, you must ensure that **bpb**=off > if > +you wish to maintain migration compatibility with existing guests, or take > +steps to reboot guests with **bpb** enabled prior to migrating them. This paragraph confuses me a bit. Both bpb and ppa15 are guest visible, aren't they?