Re: [v2] powerpc/xics,icp-opal: Fix CPPR setting for icp-opal

On Fri, 2017-03-03 at 00:58:44 UTC, Balbir Singh wrote:

CPPR (Current Processor Priority Register) emulation on icp-opal
uses a single priority in the backend and that can cause CPU
hotplug to be affected when we try to send an IPI to it.

The fix is in migrate_irqs_away, the fix does the following:

1. It moves the setting of CPPR to after all IRQ migration
   is complete
2. In icp-opal, we ignore masking the CPPR when the CPPR
is set to default priority, anything else we just pass
through

Right now this fix is designed with backporting to stable
in mind

We'll need a newer version of this later when we merge the
DEFAULT and IPI priorities to the same value in the kernel.

Fixes: d74361881f0d ("powerpc/xics: Add ICP OPAL backend")
Cc: stable@vger.kernel.org (v4.8+)

Testing

1. I've tested this fix on a virtual partition running under
   kvm
2. Gautham and Vaidy have done some testing on an system that
   uses the OPAL backend
3. I've also tested this on a system with a native XICS controller

Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Reported-by: Vaidyanathan Srinivasan <redacted>
Tested-by: Vaidyanathan Srinivasan <redacted>
Signed-off-by: Balbir Singh <bsingharora@gmail.com>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/a69e2fb70350a66f91175cd2625f1e

cheers