Re: preparations for 4.9.2 and 4.7.5

From: Julien Grall <julien.grall@arm.com>
To: Stefano Stabellini <sstabellini@kernel.org>
Cc: Lars Kurth <lars.kurth@citrix.com>, Wei Liu <wei.liu2@citrix.com>,
	Ian Jackson <Ian.Jackson@eu.citrix.com>,
	andre.przywara@linaro.org, Jan Beulich <JBeulich@suse.com>,
	xen-devel <xen-devel@lists.xenproject.org>,
	nd@arm.com
Subject: Re: preparations for 4.9.2 and 4.7.5
Date: Fri, 16 Mar 2018 16:56:06 +0000	[thread overview]
Message-ID: <81eb8430-e104-1f37-38ae-b9dffbf2f2cb@arm.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1803160929540.15548@sstabellini-ThinkPad-X260>

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

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel