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

[Michael Ellerman]

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 We'll need a newer version of this later when we merge the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 at 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 at ellerman.id.au>
> Reported-by: Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com>
> Tested-by: Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com>
> Signed-off-by: Balbir Singh <bsingharora at gmail.com>

Applied to powerpc fixes, thanks.

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

cheers