On 13 March 2018 at 10:38, Greg KH firstname.lastname@example.org wrote:
On Tue, Mar 13, 2018 at 10:13:26AM +0000, Ard Biesheuvel wrote:
On 13 March 2018 at 10:04, Greg KH email@example.com wrote:
On Wed, Mar 07, 2018 at 06:24:09PM +0000, Ard Biesheuvel wrote:
On 2 March 2018 at 16:54, Greg KH firstname.lastname@example.org wrote:
Please test on the hardware that is affected, otherwise you do not know if your patches do anything or not.
I don't think it is feasible to test these backports by confirming that they make the fundamental issue go away. We simply don't have the code to reproduce all the variants, and we have to rely on the information provided by ARM Ltd. regarding which cores are affected and which aren't.
You really don't have the reproducers? Please work with ARM to resolve that, this should not be a non-tested set of patches. That's really worse than no patches at all, as if they were applied, that would provide a false-sense of "all is fixed".
I know that on x86, the line between architecture and platform is blurry. That is not the case on ARM, though.
Unlike platform firmware, the OS is built on top of an abstracted platform which is described by ARM's Architecture Reference Manual. If ARM Ltd. issues recommendations regarding what firmware PSCI methods to call when doing a context switch, or which barrier instruction to issue in certain circumstances, they do so because a certain class of hardware may require it in some cases. It is really not up to me to go find some exploit code on GitHub, run it before and after applying the patch and conclude that the problem is fixed. Instead, what I should do is confirm that the changes result in the recommended actions to be taken at the appropriate times.
To _not_ take that exploit code and run it to _verify_ that your patches work, would be foolish, right?
Oh, absolutely. But that presupposes access to both the affected hardware and the exploit code.
I can't believe we are having the argument of "Test that your patches actually work"...
Ugh, these series are all now dropped from my patch queue until you all get your act together and get someone to verify the changes actually work.
Fair enough. If anyone needs these patches for their systems, they can respond with a Tested-by: