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Subject: Re: [PATCH 3.18 16/90] cpupower: Fix coredump on VMWare
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org
Cc:     stable@vger.kernel.org, Shuah Khan <shuah@kernel.org>,
        Stafford Horne <shorne@gmail.com>,
        Sasha Levin <sashal@kernel.org>
References: <20181119162620.585061184@linuxfoundation.org>
 <20181119162623.516060898@linuxfoundation.org>
From:   Prarit Bhargava <prarit@redhat.com>
Message-ID: <c2d0d4ab-a9e5-cc7b-55d9-f99754beff55@redhat.com>
Date:   Mon, 19 Nov 2018 13:11:54 -0500
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On 11/19/2018 11:28 AM, Greg Kroah-Hartman wrote:
> 3.18-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Prarit Bhargava <prarit@redhat.com>
> 
> [ Upstream commit f69ffc5d3db8f1f03fd6d1df5930f9a1fbd787b6 ]

Greg, as previously mentioned to Sasha, this patch also needs 8c22e2f69592
("cpupower: Fix AMD Family 0x17 msr_pstate size").  I did not see a message
indicating that 8c22e2f69592 was also being backported to 3.18-stable.  My
apologies if I missed it.

P.


> 
> cpupower crashes on VMWare guests.  The guests have the AMD PStateDef MSR
> (0xC0010064 + state number) set to zero.  As a result fid and did are zero
> and the crash occurs because of a divide by zero (cof = fid/did).  This
> can be prevented by checking the enable bit in the PStateDef MSR before
> calculating cof.  By doing this the value of pstate[i] remains zero and
> the value can be tested before displaying the active Pstates.
> 
> Check the enable bit in the PstateDef register for all supported families
> and only print out enabled Pstates.
> 
> Signed-off-by: Prarit Bhargava <prarit@redhat.com>
> Cc: Shuah Khan <shuah@kernel.org>
> Cc: Stafford Horne <shorne@gmail.com>
> Signed-off-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
>  tools/power/cpupower/utils/cpufreq-info.c |    2 ++
>  tools/power/cpupower/utils/helpers/amd.c  |    5 +++++
>  2 files changed, 7 insertions(+)
> 
> --- a/tools/power/cpupower/utils/cpufreq-info.c
> +++ b/tools/power/cpupower/utils/cpufreq-info.c
> @@ -200,6 +200,8 @@ static int get_boost_mode(unsigned int c
>  		printf(_("    Boost States: %d\n"), b_states);
>  		printf(_("    Total States: %d\n"), pstate_no);
>  		for (i = 0; i < pstate_no; i++) {
> +			if (!pstates[i])
> +				continue;
>  			if (i < b_states)
>  				printf(_("    Pstate-Pb%d: %luMHz (boost state)"
>  					 "\n"), i, pstates[i]);
> --- a/tools/power/cpupower/utils/helpers/amd.c
> +++ b/tools/power/cpupower/utils/helpers/amd.c
> @@ -103,6 +103,11 @@ int decode_pstates(unsigned int cpu, uns
>  		}
>  		if (read_msr(cpu, MSR_AMD_PSTATE + i, &pstate.val))
>  			return -1;
> +		if ((cpu_family == 0x17) && (!pstate.fam17h_bits.en))
> +			continue;
> +		else if (!pstate.bits.en)
> +			continue;
> +
>  		pstates[i] = get_cof(cpu_family, pstate);
>  	}
>  	*no = i;
> 
>