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

[Julien Grall <julien.grall@xxxxxxx>]

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.
Cheers,

[1] 
https://lists.xenproject.org/archives/html/xen-devel/2018-03/msg01161.html
Cheers,

--
Julien Grall

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