| Message ID | 1507553734-27854-4-git-send-email-vladimir.murzin@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Vladimir, On 09/10/17 13:55, Vladimir Murzin wrote: > There are cases when activating of Common Not Private (CNP) feature > might not be desirable; this patch allows to forcefully disable CNP > even it is supported by hardware. > > Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com> > --- > Documentation/admin-guide/kernel-parameters.txt | 4 ++++ > arch/arm64/kernel/cpufeature.c | 20 +++++++++++++++++++- > 2 files changed, 23 insertions(+), 1 deletion(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 0549662..3c1e45d 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -2560,6 +2560,10 @@ > > noclflush [BUGS=X86] Don't use the CLFLUSH instruction > > + nocnp [ARM64] > + Disable CNP (Common not Private translations) > + even if it is supported by processor. > + > nodelayacct [KNL] Disable per-task delay accounting > > nodsp [SH] Disable hardware DSP at boot time. > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index 8d098a1..724fd93 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -771,6 +771,24 @@ static bool has_no_hw_prefetch(const struct arm64_cpu_capabilities *entry, int _ > MIDR_CPU_VAR_REV(1, MIDR_REVISION_MASK)); > } > > +static bool nocnp; > + > +static int __init early_nocnp(char *p) > +{ > + nocnp = true; > + return 0; > +} > +early_param("nocnp", early_nocnp); > + > +static bool has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope) > +{ > + if (!has_cpuid_feature(entry, scope)) > + return false; > + > + return nocnp ? false : true; This feels a bit odd. Wouldn't the following be better? return !nocnp; Or simply the whole function as: return has_cpuid_feature(entry, scope) && !nocnp; Thanks, > +} > + > + > static bool runs_at_el2(const struct arm64_cpu_capabilities *entry, int __unused) > { > return is_kernel_in_hyp_mode(); > @@ -905,7 +923,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = { > .desc = "Common not Private translations", > .capability = ARM64_HAS_CNP, > .def_scope = SCOPE_SYSTEM, > - .matches = has_cpuid_feature, > + .matches = has_useable_cnp, > .sys_reg = SYS_ID_AA64MMFR2_EL1, > .sign = FTR_UNSIGNED, > .field_pos = ID_AA64MMFR2_CNP_SHIFT, >
Hi Julien, On 10/10/17 15:36, Julien Thierry wrote: > Hi Vladimir, > > On 09/10/17 13:55, Vladimir Murzin wrote: >> There are cases when activating of Common Not Private (CNP) feature >> might not be desirable; this patch allows to forcefully disable CNP >> even it is supported by hardware. >> >> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com> >> --- >> Documentation/admin-guide/kernel-parameters.txt | 4 ++++ >> arch/arm64/kernel/cpufeature.c | 20 +++++++++++++++++++- >> 2 files changed, 23 insertions(+), 1 deletion(-) >> >> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >> index 0549662..3c1e45d 100644 >> --- a/Documentation/admin-guide/kernel-parameters.txt >> +++ b/Documentation/admin-guide/kernel-parameters.txt >> @@ -2560,6 +2560,10 @@ >> noclflush [BUGS=X86] Don't use the CLFLUSH instruction >> + nocnp [ARM64] >> + Disable CNP (Common not Private translations) >> + even if it is supported by processor. >> + >> nodelayacct [KNL] Disable per-task delay accounting >> nodsp [SH] Disable hardware DSP at boot time. >> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c >> index 8d098a1..724fd93 100644 >> --- a/arch/arm64/kernel/cpufeature.c >> +++ b/arch/arm64/kernel/cpufeature.c >> @@ -771,6 +771,24 @@ static bool has_no_hw_prefetch(const struct arm64_cpu_capabilities *entry, int _ >> MIDR_CPU_VAR_REV(1, MIDR_REVISION_MASK)); >> } >> +static bool nocnp; >> + >> +static int __init early_nocnp(char *p) >> +{ >> + nocnp = true; >> + return 0; >> +} >> +early_param("nocnp", early_nocnp); >> + >> +static bool has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope) >> +{ >> + if (!has_cpuid_feature(entry, scope)) >> + return false; >> + >> + return nocnp ? false : true; > > This feels a bit odd. > > Wouldn't the following be better? > return !nocnp; > > Or simply the whole function as: > return has_cpuid_feature(entry, scope) && !nocnp; > I have no strong opinion on that, so I'll change per your suggestion. Cheers Vladimir > Thanks, > >> +} >> + >> + >> static bool runs_at_el2(const struct arm64_cpu_capabilities *entry, int __unused) >> { >> return is_kernel_in_hyp_mode(); >> @@ -905,7 +923,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = { >> .desc = "Common not Private translations", >> .capability = ARM64_HAS_CNP, >> .def_scope = SCOPE_SYSTEM, >> - .matches = has_cpuid_feature, >> + .matches = has_useable_cnp, >> .sys_reg = SYS_ID_AA64MMFR2_EL1, >> .sign = FTR_UNSIGNED, >> .field_pos = ID_AA64MMFR2_CNP_SHIFT, >> >
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 0549662..3c1e45d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2560,6 +2560,10 @@ noclflush [BUGS=X86] Don't use the CLFLUSH instruction + nocnp [ARM64] + Disable CNP (Common not Private translations) + even if it is supported by processor. + nodelayacct [KNL] Disable per-task delay accounting nodsp [SH] Disable hardware DSP at boot time. diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 8d098a1..724fd93 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -771,6 +771,24 @@ static bool has_no_hw_prefetch(const struct arm64_cpu_capabilities *entry, int _ MIDR_CPU_VAR_REV(1, MIDR_REVISION_MASK)); } +static bool nocnp; + +static int __init early_nocnp(char *p) +{ + nocnp = true; + return 0; +} +early_param("nocnp", early_nocnp); + +static bool has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope) +{ + if (!has_cpuid_feature(entry, scope)) + return false; + + return nocnp ? false : true; +} + + static bool runs_at_el2(const struct arm64_cpu_capabilities *entry, int __unused) { return is_kernel_in_hyp_mode(); @@ -905,7 +923,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = { .desc = "Common not Private translations", .capability = ARM64_HAS_CNP, .def_scope = SCOPE_SYSTEM, - .matches = has_cpuid_feature, + .matches = has_useable_cnp, .sys_reg = SYS_ID_AA64MMFR2_EL1, .sign = FTR_UNSIGNED, .field_pos = ID_AA64MMFR2_CNP_SHIFT,
There are cases when activating of Common Not Private (CNP) feature might not be desirable; this patch allows to forcefully disable CNP even it is supported by hardware. Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com> --- Documentation/admin-guide/kernel-parameters.txt | 4 ++++ arch/arm64/kernel/cpufeature.c | 20 +++++++++++++++++++- 2 files changed, 23 insertions(+), 1 deletion(-)