Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Wed, 15 Feb 2023 15:55:33 +0100 | Subject | Re: [PATCH] cpufreq: amd_pstate: Fix invalid write to MSR_AMD_CPPC_REQ |
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On Wed, Feb 15, 2023 at 1:35 PM Huang Rui <ray.huang@amd.com> wrote: > > On Tue, Feb 14, 2023 at 03:58:11PM +0800, Karny, Wyes wrote: > > `amd_pstate_set_epp` function uses `cppc_req_cached` and `epp` variable > > to update the MSR_AMD_CPPC_REQ register for AMD MSR systems. The recent > > commit 7cca9a9851a5 ("cpufreq: amd-pstate: avoid uninitialized variable > > use") changed the sequence of updating cppc_req_cached and writing the > > MSR_AMD_CPPC_REQ. Therefore while switching from powersave to > > performance governor and vice-versa in active mode MSR_AMD_CPPC_REQ is > > set with the previous cached value. To fix this: first update the > > `cppc_req_cached` variable and then call `amd_pstate_set_epp` function. > > > > - Before commit 7cca9a9851a5 ("cpufreq: amd-pstate: avoid uninitialized > > variable use"): > > > > With powersave governor: > > [ 1.652743] amd_pstate_epp_init: writing to cppc_req_cached = 0x1eff > > [ 1.652744] amd_pstate_set_epp: writing cppc_req_cached = 0x1eff > > [ 1.652746] amd_pstate_set_epp: writing min_perf = 30, des_perf = 0, max_perf = 255, epp = 0 > > > > Changing to performance governor: > > [ 300.493842] amd_pstate_epp_init: writing to cppc_req_cached = 0xffff > > [ 300.493846] amd_pstate_set_epp: writing cppc_req_cached = 0xffff > > [ 300.493847] amd_pstate_set_epp: writing min_perf = 255, des_perf = 0, max_perf = 255, epp = 0 > > > > - After commit 7cca9a9851a5 ("cpufreq: amd-pstate: avoid uninitialized > > variable use"): > > > > With powersave governor: > > [ 1.646037] amd_pstate_set_epp: writing cppc_req_cached = 0xffff > > [ 1.646038] amd_pstate_set_epp: writing min_perf = 255, des_perf = 0, max_perf = 255, epp = 0 > > [ 1.646042] amd_pstate_epp_init: writing to cppc_req_cached = 0x1eff > > > > Changing to performance governor: > > [ 687.117401] amd_pstate_set_epp: writing cppc_req_cached = 0x1eff > > [ 687.117405] amd_pstate_set_epp: writing min_perf = 30, des_perf = 0, max_perf = 255, epp = 0 > > [ 687.117419] amd_pstate_epp_init: writing to cppc_req_cached = 0xffff > > > > - After this fix: > > > > With powersave governor: > > [ 2.525717] amd_pstate_epp_init: writing to cppc_req_cached = 0x1eff > > [ 2.525720] amd_pstate_set_epp: writing cppc_req_cached = 0x1eff > > [ 2.525722] amd_pstate_set_epp: writing min_perf = 30, des_perf = 0, max_perf = 255, epp = 0 > > > > Changing to performance governor: > > [ 3440.152468] amd_pstate_epp_init: writing to cppc_req_cached = 0xffff > > [ 3440.152473] amd_pstate_set_epp: writing cppc_req_cached = 0xffff > > [ 3440.152474] amd_pstate_set_epp: writing min_perf = 255, des_perf = 0, max_perf = 255, epp = 0 > > > > Fixes: 7cca9a9851a5 ("cpufreq: amd-pstate: avoid uninitialized variable use") > > Signed-off-by: Wyes Karny <wyes.karny@amd.com> > > That's really nice catch! Thanks Wyes. > > Acked-by: Huang Rui <ray.huang@amd.com>
Applied, thanks!
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