linux-kernel - Re: [PATCH] arm64: cpufeature: Enable Qualcomm erratas

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Message-ID: <20191029170633.GX571@minitux>
Date:   Tue, 29 Oct 2019 10:06:33 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     will@...nel.org, catalin.marinas@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, stable@...r.kernel.org,
        broonie@...nel.org
Subject: Re: [PATCH] arm64: cpufeature: Enable Qualcomm erratas

On Tue 29 Oct 05:04 PDT 2019, Suzuki K Poulose wrote:

> On 10/29/2019 11:39 AM, Will Deacon wrote:
> > On Mon, Oct 28, 2019 at 11:04:32PM -0700, Bjorn Andersson wrote:
> > > With the introduction of 'cce360b54ce6 ("arm64: capabilities: Filter the
> > > entries based on a given mask")' the Qualcomm erratas are no long
> > > applied.
> > > 
> > > The result of not applying errata 1003 is that MSM8996 runs into various
> > > RCU stalls and fails to boot most of the times.
> > > 
> > > Give both 1003 and 1009 a "type" to ensure they are not filtered out in
> > > update_cpu_capabilities().
> > 
> > Oh nasty. Thanks for debugging and fixing this.
> > 
> > > Fixes: cce360b54ce6 ("arm64: capabilities: Filter the entries based on a given mask")
> > > Cc: stable@...r.kernel.org
> > > Reported-by: Mark Brown <broonie@...nel.org>
> > > Suggested-by: Will Deacon <will@...nel.org>
> > > Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> > > ---
> > >   arch/arm64/kernel/cpu_errata.c | 2 ++
> > >   1 file changed, 2 insertions(+)
> > > 
> > > diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> > > index df9465120e2f..cdd8df033536 100644
> > > --- a/arch/arm64/kernel/cpu_errata.c
> > > +++ b/arch/arm64/kernel/cpu_errata.c
> > > @@ -780,6 +780,7 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
> > >   	{
> > >   		.desc = "Qualcomm Technologies Falkor/Kryo erratum 1003",
> > >   		.capability = ARM64_WORKAROUND_QCOM_FALKOR_E1003,
> > > +		.type = ARM64_CPUCAP_SCOPE_LOCAL_CPU,
> > >   		.matches = cpucap_multi_entry_cap_matches,
> > 
> > This should probably be ARM64_CPUCAP_LOCAL_CPU_ERRATUM instead, but I'll
> > want Suzuki's ack before I take the change.
> 
> Yes, it must be ARM64_CPUCAP_LOCAL_CPU_ERRATUM.
> 

Thanks, will fix.

> It may be a good idea to stick in a check to make sure that the scope is
> set for all the capabilities in a separate patch. e.g,
> 
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index d260e3bdf07b..51a79b4a44eb 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -546,6 +546,8 @@ static void __init
>  init_cpu_hwcaps_indirect_list_from_array(const struct
> arm64_cpu_capabilities *caps)
>  {
>  	for (; caps->matches; caps++) {
> +		WARN(!cpucap_default_scope(caps),
> +		     "Invalid scope for capability %d\n", caps->capability);
>  		if (WARN(caps->capability >= ARM64_NCAPS,
>  			"Invalid capability %d\n", caps->capability))
> 			continue;

In hindsight this would have saved me a considerable amount of time, so
I like this proposal!

Regards,
Bjorn

> 
> Otherwise looks good to me.
> 
> > >   		.match_list = qcom_erratum_1003_list,
> > >   	},
> > > @@ -788,6 +789,7 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
> > >   	{
> > >   		.desc = "Qualcomm erratum 1009, ARM erratum 1286807",
> > >   		.capability = ARM64_WORKAROUND_REPEAT_TLBI,
> > > +		.type = ARM64_CPUCAP_SCOPE_LOCAL_CPU,
> > >   		ERRATA_MIDR_RANGE_LIST(arm64_repeat_tlbi_cpus),
> > 
> > ERRATA_MIDR_RANGE_LIST sets the type already, so I think this is redundant.
> > 
> > Will
> > 
> 
> 
> 
> Cheers
> Suzuki