On Wed, Sep 6, 2023 at 9:08 PM Srinivas Pandruvada srinivas.pandruvada@linux.intel.com wrote:

System runs at minimum performance, once powercap RAPL package domain enabled flag is changed from 1 to 0 to 1.

Setting RAPL package domain enabled flag to 0, results in setting of power limit 4 (PL4) MSR 0x601 to 0. This implies disabling PL4 limit. The PL4 limit controls the peak power. So setting 0, results in some undesirable performance, which depends on hardware implementation.

Even worse, when the enabled flag is set to 1 again. This will set PL4 MSR value to 0x01, which means reduce peak power to 0.125W. This will force system to run at the lowest possible performance on every PL4 supported system.

Setting enabled flag should only affect the "enable" bit, not other bits. Here it is changing power limit.

This is caused by a change which assumes that there is an enable bit in the PL4 MSR like other power limits. Although PL4 enable/disable bit is present with TPMI RAPL interface, it is not present with the MSR interface.

There is a rapl_primitive_info defined for non existent PL4 enable bit and then it is used with the commit 9050a9cd5e4c ("powercap: intel_rapl: Cleanup Power Limits support") to enable PL4. This is wrong, hence remove this rapl primitive for PL4. Also in the function rapl_detect_powerlimit(), PL_ENABLE is used to check for the presence of power limits. Replace PL_ENABLE with PL_LIMIT, as PL_LIMIT must be present. Without this change, PL4 controls will not be available in the sysfs once rapl primitive for PL4 is removed.

Fixes: 9050a9cd5e4c ("powercap: intel_rapl: Cleanup Power Limits support") Suggested-by: Zhang Rui rui.zhang@intel.com Signed-off-by: Srinivas Pandruvada srinivas.pandruvada@linux.intel.com Tested-by: Sumeet Pawnikar sumeet.r.pawnikar@intel.com Cc: stable@vger.kernel.org # v6.5+

---

v2

• Remove RAPL primitive for PL4 instead as suggedted by Rui
• Replace PL_ENABLE with PL_LIMIT for domain detect
• Update change log and header

drivers/powercap/intel_rapl_common.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/powercap/intel_rapl_common.c b/drivers/powercap/intel_rapl_common.c index 5c2e6d5eea2a..40a2cc649c79 100644 --- a/drivers/powercap/intel_rapl_common.c +++ b/drivers/powercap/intel_rapl_common.c @@ -658,8 +658,6 @@ static struct rapl_primitive_info rpi_msr[NR_RAPL_PRIMITIVES] = { RAPL_DOMAIN_REG_LIMIT, ARBITRARY_UNIT, 0), [PL2_CLAMP] = PRIMITIVE_INFO_INIT(PL2_CLAMP, POWER_LIMIT2_CLAMP, 48, RAPL_DOMAIN_REG_LIMIT, ARBITRARY_UNIT, 0),

•   [PL4_ENABLE] = PRIMITIVE_INFO_INIT(PL4_ENABLE, POWER_LIMIT4_MASK, 0,
  

•                           RAPL_DOMAIN_REG_PL4, ARBITRARY_UNIT, 0),
    [TIME_WINDOW1] = PRIMITIVE_INFO_INIT(TIME_WINDOW1, TIME_WINDOW1_MASK, 17,
                        RAPL_DOMAIN_REG_LIMIT, TIME_UNIT, 0),
    [TIME_WINDOW2] = PRIMITIVE_INFO_INIT(TIME_WINDOW2, TIME_WINDOW2_MASK, 49,
  

@@ -1458,7 +1456,7 @@ static void rapl_detect_powerlimit(struct rapl_domain *rd) } }

•           if (rapl_read_pl_data(rd, i, PL_ENABLE, false, &val64))
  

•           if (rapl_read_pl_data(rd, i, PL_LIMIT, false, &val64))
                    rd->rpl[i].name = NULL;
    }
  

}

Applied as 6.6-rc material, thanks!