| Message ID | 20230214075811.23644-1-wyes.karny@amd.com (mailing list archive) |
|---|---|
| State | Mainlined, archived |
| Headers | show |
| Series | cpufreq: amd_pstate: Fix invalid write to MSR_AMD_CPPC_REQ | expand |
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> > --- > drivers/cpufreq/amd-pstate.c | 25 +++++++++++++------------ > 1 file changed, 13 insertions(+), 12 deletions(-) > > diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c > index b8862afef4e4..45c88894fd8e 100644 > --- a/drivers/cpufreq/amd-pstate.c > +++ b/drivers/cpufreq/amd-pstate.c > @@ -1057,27 +1057,28 @@ static void amd_pstate_epp_init(unsigned int cpu) > > cpudata->epp_policy = cpudata->policy; > > - if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE) { > - epp = amd_pstate_get_epp(cpudata, value); > - if (epp < 0) > - goto skip_epp; > - /* force the epp value to be zero for performance policy */ > - epp = 0; > - } else { > - /* Get BIOS pre-defined epp value */ > - epp = amd_pstate_get_epp(cpudata, value); > - if (epp) > - goto skip_epp; > + /* Get BIOS pre-defined epp value */ > + epp = amd_pstate_get_epp(cpudata, value); > + if (epp < 0) { > + /** > + * This return value can only be negative for shared_memory > + * systems where EPP register read/write not supported. > + */ > + goto skip_epp; > } > + > + if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE) > + epp = 0; > + > /* Set initial EPP value */ > if (boot_cpu_has(X86_FEATURE_CPPC)) { > value &= ~GENMASK_ULL(31, 24); > value |= (u64)epp << 24; > } > > + WRITE_ONCE(cpudata->cppc_req_cached, value); > amd_pstate_set_epp(cpudata, epp); > skip_epp: > - WRITE_ONCE(cpudata->cppc_req_cached, value); > cpufreq_cpu_put(policy); > } > > -- > 2.34.1 >
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!
diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c index b8862afef4e4..45c88894fd8e 100644 --- a/drivers/cpufreq/amd-pstate.c +++ b/drivers/cpufreq/amd-pstate.c @@ -1057,27 +1057,28 @@ static void amd_pstate_epp_init(unsigned int cpu) cpudata->epp_policy = cpudata->policy; - if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE) { - epp = amd_pstate_get_epp(cpudata, value); - if (epp < 0) - goto skip_epp; - /* force the epp value to be zero for performance policy */ - epp = 0; - } else { - /* Get BIOS pre-defined epp value */ - epp = amd_pstate_get_epp(cpudata, value); - if (epp) - goto skip_epp; + /* Get BIOS pre-defined epp value */ + epp = amd_pstate_get_epp(cpudata, value); + if (epp < 0) { + /** + * This return value can only be negative for shared_memory + * systems where EPP register read/write not supported. + */ + goto skip_epp; } + + if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE) + epp = 0; + /* Set initial EPP value */ if (boot_cpu_has(X86_FEATURE_CPPC)) { value &= ~GENMASK_ULL(31, 24); value |= (u64)epp << 24; } + WRITE_ONCE(cpudata->cppc_req_cached, value); amd_pstate_set_epp(cpudata, epp); skip_epp: - WRITE_ONCE(cpudata->cppc_req_cached, value); cpufreq_cpu_put(policy); }
`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> --- drivers/cpufreq/amd-pstate.c | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-)