Re: [PATCH AUTOSEL 4.19 022/146] cpupower: Fix coredump on VMWare

Prarit Bhargava
2018-11-01T11:43:38Z

On 10/31/2018 07:03 PM, Sasha Levin wrote:
> From: Prarit Bhargava <prarit@redhat.com>
>
> [ Upstream commit f69ffc5d3db8f1f03fd6d1df5930f9a1fbd787b6 ]
>
> 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.
>

Hi Sasha,

This patch, f69ffc5d3db8, depends on 8c22e2f69592 ("cpupower: Fix AMD Family
0x17 msr_pstate size"). Without 8c22e2f69592 the patch below will always read a
value of "0" and not output the correct data.

8c22e2f69592 must be applied to any stable branch that f69ffc5d3db8 is applied to.

P.

> 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>
> ---
> tools/power/cpupower/utils/cpufreq-info.c | 2 ++
> tools/power/cpupower/utils/helpers/amd.c | 5 +++++
> 2 files changed, 7 insertions(+)
>
> diff --git a/tools/power/cpupower/utils/cpufreq-info.c b/tools/power/cpupower/utils/cpufreq-info.c
> index df43cd45d810..ccd08dd00996 100644
> --- 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 cpu)
> 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]);
> diff --git a/tools/power/cpupower/utils/helpers/amd.c b/tools/power/cpupower/utils/helpers/amd.c
> index bb41cdd0df6b..58d23997424d 100644
> --- a/tools/power/cpupower/utils/helpers/amd.c
> +++ b/tools/power/cpupower/utils/helpers/amd.c
> @@ -119,6 +119,11 @@ int decode_pstates(unsigned int cpu, unsigned int cpu_family,
> }
> 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;
>