Re: [Xen-devel] preparations for 4.9.2 and 4.7.5

[Julien Grall <julien.grall@xxxxxxx>]

Hi Stefano,

On 16/03/2018 16:33, Stefano Stabellini wrote:
> On Fri, 16 Mar 2018, Julien Grall wrote:
> > Hi Stefano,
> >
> > On 15/03/18 23:52, Stefano Stabellini wrote:
> > > On Wed, 14 Mar 2018, Stefano Stabellini wrote:
> > > > After looking at the test results, which are good for arm, and
> > > > considering that master hasn't passed yet after 2 more days, I agree
> > > > with Julien: I think we should not release 4.9.2 and 4.7.5 without the
> > > > arm64 spectre patches. At this point, I'll proceed to backport the
> > > > patches now.
> > > Julien, Andre,
> > >
> > > Please give a look at the following branches:
> > >
> > > git://xenbits.xen.org/people/sstabellini/xen-unstable.git
> > > staging-4.7-spectre
> > > git://xenbits.xen.org/people/sstabellini/xen-unstable.git
> > > staging-4.8-spectre
> > > git://xenbits.xen.org/people/sstabellini/xen-unstable.git
> > > staging-4.9-spectre
> > For all of the tree above, as I said yesterday, I clearly don't want to see
> > the smccc framework backport for Xen 4.9 and older. This is a massive changes
> > of the interface that is not necessary for spectre. My main concern is making
> > SMC instruction available to the guest.
> >
> > It would be just sufficient to emulate the few SMCCC function ID we care in
> > do_trap_psci (function can be renamed).
> >
> > This is also clearly wrong to backport coding style or code non-justified code
> > movement (sysreg) just to please the cherry-pick.
> >
> > I am also worry to bump the version of the emulated PSCI (0.2 -> 1.0) for
> > those releases. Some guests may rely on a specific version and may now
> > crashes.
> >
> > Overall, the right way to support spectre in earlier releases is custom patch
> > and only do minimal modification.
> >
> > > git://xenbits.xen.org/people/sstabellini/xen-unstable.git
> > > staging-4.10-spectre
> > The patches below should not be part of spectre nor backport to 4.10:
> >    - 82e29c87dc7f4f2a7e2f111c3646479da21a910a "ARM: remove unneeded gic.h
> > inclusions"
> >    - 79563717c9dd5383abcf0ba94d813de9b42e3793 "xen/arm: psci: Prefix with
> > static any functions not exported"
> >    - 6d0e9b21b1f7213c1994cc2d636448ee2d5372c2 "xen/arm: vpsci: Update the
> > return type for MIGRATE_INFO_TYPE"
> >
> > The patches below should not be part of spectre but candidate to 4.10:
> >    - c2d70f77cc7987be164cd87b76459782497fc540 "xen/arm: vpsci: Rework the logic
> > to start AArch32 vCPU in Thumb mode"
> >
> > You will also want to backport [1] which address a relaxation of the
> > ARM_SMCCC_ARCH_WORKAROUND_1.
> I understand your concerns, in that case could you please provide the
> git branches?
That will have to wait when I have spare cycle. Most likely somewhere in 
April when I am done from the Xen 4.11 patches and back from holidays.
So It is probably the right time to put into contribution stakeholders 
who are using those Xen 4.* stable releases.
Cheers,

[1] https://developer.arm.com/support/security-update/downloads

--
Julien Grall

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