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

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

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?

If I had to do the backports myself, I'll stick with my approach because
I am more confident of its correctness, but I would be happy to take a
look at your version of the backports.

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