linux-kernel - Re: [PATCH v4 06/10] powerpc/watchpoint: Set CPU_FTR

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Date:   Mon, 20 Jul 2020 11:39:49 +1000
From:   Jordan Niethe <jniethe5@...il.com>
To:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>, mikey@...ling.org,
        apopple@...ux.ibm.com, Paul Mackerras <paulus@...ba.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@....fr>,
        naveen.n.rao@...ux.vnet.ibm.com, peterz@...radead.org,
        jolsa@...nel.org, oleg@...hat.com, fweisbec@...il.com,
        mingo@...nel.org, pedromfc@...ibm.com, miltonm@...ibm.com,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 06/10] powerpc/watchpoint: Set CPU_FTR_DAWR1 based on
 pa-features bit

On Fri, Jul 17, 2020 at 2:10 PM Ravi Bangoria
<ravi.bangoria@...ux.ibm.com> wrote:
>
> As per the PAPR, bit 0 of byte 64 in pa-features property indicates
> availability of 2nd DAWR registers. i.e. If this bit is set, 2nd
> DAWR is present, otherwise not. Host generally uses "cpu-features",
> which masks "pa-features". But "cpu-features" are still not used for
> guests and thus this change is mostly applicable for guests only.
>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
I checked those PAPR values are correct and checked running a powernv
kernel in p10 mambo with dt_cpu_ftrs=off and it does set the
CPU_FTR_DAWR1 bit.
(using p10 skiboot).
Tested-by: Jordan Niethe <jniethe5@...il.com>
> ---
>  arch/powerpc/kernel/prom.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> index 9cc49f265c86..c76c09b97bc8 100644
> --- a/arch/powerpc/kernel/prom.c
> +++ b/arch/powerpc/kernel/prom.c
> @@ -175,6 +175,8 @@ static struct ibm_pa_feature {
>          */
>         { .pabyte = 22, .pabit = 0, .cpu_features = CPU_FTR_TM_COMP,
>           .cpu_user_ftrs2 = PPC_FEATURE2_HTM_COMP | PPC_FEATURE2_HTM_NOSC_COMP },
> +
> +       { .pabyte = 64, .pabit = 0, .cpu_features = CPU_FTR_DAWR1 },
>  };
>
>  static void __init scan_features(unsigned long node, const unsigned char *ftrs,
> --
> 2.26.2
>