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

[Julien Grall <julien.grall@xxxxxxx>]

Hi Stefano,

On 04/04/18 00:55, Stefano Stabellini wrote:
> On Tue, 3 Apr 2018, Julien Grall wrote:
> > Hi,
> >
> > On 16/03/18 17:15, Julien Grall wrote:
> > > On 16/03/2018 16:56, Julien Grall wrote:
> > > > 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.
> > > To be clear, for Xen 4.10 it is just a matter of dropping the 3 patches I
> > > suggested. There are actually no clash with the current code.
> > Gentle ping. Is there anything blocking to get those patches in Xen 4.10?
> Done! Thanks for the ping!
It looks like the commit 6b270fae7ad462687550a875f714bff18d764416 
"xen/arm: Relax ARM_SMCCC_ARCH_WORKAROUND_1 discovery" is missing in Xen 
4.10.
Cheers,

--
Julien Grall

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