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Re: [Xen-devel] RT Xen on ARM - R-Car series

On 2/4/19 10:32 AM, Andrii Anisov wrote:
Hello Julien,

Hi Andrii,

On 01.02.19 12:51, Julien Grall wrote:
I don't consider polluting your log a real problem.
Unless the system becomes an insane typewriter :)

I don't consider it as a critical issue because of the type of guest we currently support, so it is not in my queue for Xen 4.12 fixes.

Feel free to suggest it as a blocker if you think it is.
Well, for us the situation is as following: Renesas requested XEN 4.12 for the next release of their virtualization package.

That's a good news! Let me try to address your concerns below one by one.

And they employ KPTI enabled kernel in the BSP.
KPTI is going to work on Xen. There are no known issue with Linux as the virtual address is not going to be re-used for other purpose in the virtual address space. The only inconvenience is the message in debug build.

Just in case, I am not saying it should not be fixed :).

That reveals another critical issue for us, in addition to Set/Way issue

From the discussion on the another thread and with other people, this is not entirely the fault of Xen. This was a misuse of the instructions by the driver. While you may want to deal with this in your case, I would like to avoid promoting bad behavior when using Xen upstream.

and possible performance drops/irq latency raise due to specter mitigation measures.

Can you remind me the cores you are using?

Also, when you mean possible, does it mean you haven't looked the performance regression?

I'm not sure if this is sufficient a justification to make it the release blocker, but we are up to this stuff.

Which one?


Julien Grall

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