From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51870) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eltgH-0006VU-3f for qemu-devel@nongnu.org; Wed, 14 Feb 2018 04:48:50 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eltgD-00040C-VE for qemu-devel@nongnu.org; Wed, 14 Feb 2018 04:48:49 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:39922 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eltgD-0003zz-Oh for qemu-devel@nongnu.org; Wed, 14 Feb 2018 04:48:45 -0500 References: <20180214001105.21508-1-mdroth@linux.vnet.ibm.com> <20180214101128.1bc889ea.cohuck@redhat.com> <9b9488c4-3c7d-3743-2e6d-e094b3281994@de.ibm.com> From: David Hildenbrand Message-ID: <48d4324f-ec0c-8027-7f4f-afb406451367@redhat.com> Date: Wed, 14 Feb 2018 10:48:42 +0100 MIME-Version: 1.0 In-Reply-To: <9b9488c4-3c7d-3743-2e6d-e094b3281994@de.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [qemu-web PATCH] Add a blog post documenting Spectre/Meltdown options for QEMU 2.11.1 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Christian Borntraeger , Cornelia Huck , Michael Roth Cc: qemu-devel@nongnu.org, Eduardo Habkost , Paolo Bonzini , Peter Maydell , Suraj Jitindar Singh , David Gibson , Thomas Huth On 14.02.2018 10:18, Christian Borntraeger wrote: > > > On 02/14/2018 10:11 AM, Cornelia Huck wrote: >> On Tue, 13 Feb 2018 18:11:05 -0600 >> Michael Roth 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 >>> Cc: Paolo Bonzini >>> Cc: Peter Maydell >>> Cc: Suraj Jitindar Singh >>> Cc: David Gibson >>> Cc: Christian Borntraeger >>> Cc: Cornelia Huck >>> Cc: Thomas Huth >>> Signed-off-by: Michael Roth >>> --- >>> >>> 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? > > full model is just an internal implementation. > Either use > - host passthrough > - host model > - add bpb and ppa15 manually to the choosen model (e.g. z13,bpb=on,ppa15=on) Ack. They won't be enabled by existing base (e.g. z13-base) or default (e.g. z13) CPU models. The full models are internal only. So "-cpu host" or "-cpu [MODEL],bpb=on,ppa15=on" are the only two options on the QEMU command line level. -- Thanks, David / dhildenb