On 11/23/18 6:09 AM, Marc Zyngier wrote:
Hi Hanjun,
On 23/11/2018 09:40, Hanjun Guo wrote:
Hi Marc,
On 2018/11/23 17:10, Marc Zyngier wrote:
On 23/11/2018 01:25, Hanjun Guo wrote:
On 2018/10/31 22:04, David Long wrote:
From: "David A. Long" <dave.long@xxxxxxxxxx>
V4.4 backport of spectre patches from Russell M. King's spectre branch.
Most KVM patches are excluded. Patches not yet in upstream are excluded.
I tested this patch set on top of stable 4.4 kernel, running on boards with
A9 and A15 based Hisilicon SoCs, didn't see boot regression and other function
regressions in our CI system,
Tested-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
Since this patch set didn't include PSCI based hardening for arm32, so
bugfix 6282e916f774 ("ARM: 8809/1: proc-v7: fix Thumb annotation of
cpu_v7_hvc_switch_mm") is not needed for this patch set and this patch
set is in a good shape I think. So what's the plan for this patch set?
Well, not having these patches means that a 32bit kernel won't be get
any Spectre-v2 mitigation when run as a guest on an arm64 platform. It
turns out that this is a pretty common setup among people building large
pieces of SW, such as distributions.
I almost miss this point, that makes sense to me :)
I've been watching arm32 spectre patches appear since September and I
have a work item to backport these too in the near future. I've been
trying to focus on backporting 64-bit security patches to v4.4 in the
short term though.
Not having KVM host mitigation on 32bit ARM is probably OK (let's face
it, I'm the only user), but not mitigating it as a guest doesn't seem
completely OK to me.
We are working on a patch set which is backported from mainline to fix
ARM64 spectre-v1, spectre-v2 and SSBD for stable 4.4 kernel, and that
patch set (almost done) has PSCI patches which is needed by 32bit ARM,
so how about posting those ARM64 spectre fixes then backport all those
kvm patches for 32bit ARM spectre fix as well?
I'm not sure I get what you mean by PSCI. PSCI is not involved in the
Spectre-v2 mitigation, as we use a specially designed SMC call, relying
on the SMCCC 1.1 infrastructure. Maybe it is what you're referring to here?
Again, I don't think it is worth the hassle backporting the KVM patches.
What I'd like to see is the guest (and bare metal) support code that
uses the ARCH_WORKAROUND_1 SMCCC 1.1 infrastructure.
I also don't think it is worth creating an artificial dependency between
the two architectures. Yes, some patches are common (the SMCCC
infrastructure), but that can be easily be solved at merge time. My vote
would be for David to carry the relevant patches in this series.
Thanks,
M.
I will look at what this means for a new patch set. I'm concerned about
how much infrastructure this might mean backporting to v4.4, but I don't
have enough familiarity with the code yet to know if that's a valid concern.
-dl
