linux-kernel - Re: Relax CPU features sanity checking on heterogeneous architectures

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Message-ID: <20191011143442.515659f4@why>
Date:   Fri, 11 Oct 2019 14:34:42 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Cc:     Mark Rutland <mark.rutland@....com>, rnayak@...eaurora.org,
        suzuki.poulose@....com, catalin.marinas@....com,
        linux-arm-kernel <linux-arm-kernel-bounces@...ts.infradead.org>,
        linux-kernel@...r.kernel.org, jeremy.linton@....com,
        bjorn.andersson@...aro.org, linux-arm-msm@...r.kernel.org,
        andrew.murray@....com, will@...nel.org, Dave.Martin@....com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: Relax CPU features sanity checking on heterogeneous
 architectures

On Fri, 11 Oct 2019 18:47:39 +0530
Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org> wrote:

> Hi Mark,
> 
> Thanks a lot for the detailed explanations, I did have a look at all the variations before posting this.
> 
> On 2019-10-11 16:20, Mark Rutland wrote:
> > Hi,
> > 
> > On Fri, Oct 11, 2019 at 11:19:00AM +0530, Sai Prakash Ranjan wrote:  
> >> On latest QCOM SoCs like SM8150 and SC7180 with big.LITTLE arch, below
> >> warnings are observed during bootup of big cpu cores.  
> > 
> > For reference, which CPUs are in those SoCs?
> >   
> 
> SM8150 is based on Cortex-A55(little cores) and Cortex-A76(big cores). I'm afraid I cannot give details about SC7180 yet.
> 
> >> SM8150:  
> >> >> [    0.271177] CPU features: SANITY CHECK: Unexpected variation in  
> >> SYS_ID_AA64PFR0_EL1. Boot CPU: 0x00000011112222, CPU4: >> 0x00000011111112  
> > 
> > The differing fields are EL3, EL2, and EL1: the boot CPU supports
> > AArch64 and AArch32 at those exception levels, while the secondary only
> > supports AArch64.
> > 
> > Do we handle this variation in KVM?  
> 
> We do not support KVM.

Mainline does. You don't get to pick and choose what is supported or
not.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...