From mboxrd@z Thu Jan  1 00:00:00 1970
From: Suzuki.Poulose@arm.com (Suzuki K. Poulose)
Date: Mon, 7 Mar 2016 17:22:12 +0000
Subject: ARM64: CPU Hotplug: can't enable more cpus than maxcpus value
 (kernel 4.5)
In-Reply-To: <56D85B37.8020306@arm.com>
References: <20160303141752.GA12255@localhost.localdomain>
 <20160303144215.GC19139@leverpostej> <56D85151.9050607@arm.com>
 <20160303151200.GE19139@leverpostej> <56D85B37.8020306@arm.com>
Message-ID: <56DDB8C4.5010703@arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 03/03/16 15:41, Suzuki K. Poulose wrote:
> On 03/03/16 15:12, Mark Rutland wrote:
>> On Thu, Mar 03, 2016 at 02:59:29PM +0000, Suzuki K. Poulose wrote:
>>> On 03/03/16 14:42, Mark Rutland wrote:
>>> We don't have this limitation anymore, as we can check if the booting CPU
>>> has any conflicting/missing features w.r.t the established set and fail the
>>> booting if it does.
>>
>> While we do this, that's more of a last-ditch effort as opposed to a
>> general solution, and I'm not sure it's complete.
>>
>> What happens when we online a CPU that we determine needs a new erratum
>> workaround applied? I didn't think we prohibited onlining in that case.
>
> Right, the erratas can't be applied, as we would have free'd them already.

We could do what we now do for the CPU features though, i.e, fail any CPUs
which has an ERRATA that hasn't been applied in the kernel at boot time.

Cheers
Suzuki